1Vectors_params(3NCARG) NCAR GRAPHICS Vectors_params(3NCARG)
2
6 Vectors_params - This document briefly describes all Vectors internal
7 parameters.
8
10 Parameter descriptions follow, in alphabetical order. Each description
11 begins with a line giving the three-character mnemonic name of the
12 parameter, the phrase for which the mnemonic stands, the intrinsic type
13 of the parameter, and an indication of whether or not it is an array.
14 ACM - Arrow Color Mode - Integer
16 ACM controls how color is applied to filled vector arrows. It
18 applies only when AST has the value 1. Its behavior also depends
19 on the setting of the parameter CTV. Assuming that CTV is set to
20 a non-zero value, implying that multi-colored vectors are
21 desired, ACM has the following settings:
22 Value Effect
26 ----- ------
27 -2 Multi-colored fill; outline off
28 -1 Fill off; multi-colored outline
29 0 Multi-colored fill; mono-colored outline
30 1 Mono-colored fill; multi-colored outline
31 2 Multi-colored fill; multi-colored outline
32 Mono-colored outlines use the current GKS polyline color index.
34 Mono-colored fill uses the current GKS fill color index. When
35 CTV is set to 0, both the fill and the outlines become mono-
36 colored, and therefore only modes -2, -1, and 0 remain
37 distinguishable. The default value is 0.
38 AFO - Arrow Fill Over Arrow Lines - Integer
40 If AFO is set to 1, the perimeter outline of a filled vector
41 arrow is drawn first, underneath the fill. In this case, you
42 must set the line thickness parameter (LWD) to a value greater
43 than unity in order for the line to appear completely. The
44 advantage of drawing the line underneath is that the full extent
45 of the fill appears, resulting in a crisper, more sharply
46 defined arrow; when the line is drawn on top of the fill using a
47 different color index, the fill color may be partially or
48 completely obscured, especially for small vector arrows. AFO has
49 an effect only when the parameter AST is set to 1. The default
50 value of AFO is 1.
51 AIR - Arrow Interior Reference Fraction - Real
53 AIR specifies the distance from the point of the arrowhead of a
54 filled vector arrow drawn at the reference length to the point
55 where the arrowhead joins with the line extending to the tail of
56 the arrow. Its value represents a fraction of the reference
57 length. This distance is adjusted proportionally to the X
58 component of the arrowhead size for vector arrows whose length
59 differs from the reference length. See VRL for an explanation
60 of how the reference length is determined. AIR has an effect
61 only when AST is set to 1. AIR is allowed to vary between 0.0
62 and 1.0 and its default value is 0.33.
63 AMN - Arrow Head Minimum Size - Real
65 Specifies a minimum length for the two lines representing the
66 point of the vector arrow head, as a fraction of the viewport
67 width. AMN has an effect only for line-drawn vector arrows
68 (parameter AST set to 0). Normally the arrow head size is scaled
69 proportionally to the length of the vector. This parameter
70 allows you to ensure that the arrow head will remain
71 recognizable even for very short vectors. Note that you can
72 cause all the arrowheads in the plot to be drawn at the same
73 size if you set AMN and AMX to the same value. If you set both
74 AMN and AMX to 0.0 the arrowheads will not be drawn at all. The
75 default value is 0.005.
76 AMX - Arrow Head Maximum Size - Real
78 Specifies a maximum length for the two lines representing the
79 point of the vector arrow head, as a fraction of the viewport
80 width. AMX has an effect only for line-drawn vector arrows
81 (parameter AST set to 0). Normally the arrow head is scaled
82 proportionally to the length of the vector. This parameter
83 allows you to ensure that the arrow heads do not become
84 excessively large for high magnitude vectors. Note that you can
85 cause all the arrowheads in the plot to be drawn at the same
86 size if you set AMN and AMX to the same value. If you set both
87 AMN and AMX to 0.0 the arrowheads will not be drawn at all. The
88 default value is 0.05.
89 AST - Arrow Style - Integer
91 If AST is set to 0, the vector arrows are drawn using lines
93 only. When AST is set to 1, the vectors are plotted using
94 variable width filled arrows, with an optional outline. If AST
95 is set to 2, wind barb glyphs are used to represent the
96 vectors.There are parameters for controlling the appearance of
97 each style. These have an effect only for one value of AST.
98 However, certain parameters apply to all arrow styles. Here is a
99 table of parameters that affect the appearance of vectors and
100 how their behavior is affected by the setting of AST:
101 Parameter Line-Drawn Arrows Filled Arrows Wind Barbs
104 --------- ----------------- ------------- ----------
105 ACM x
106 AFO x
107 AIR x
108 AMN x
109 AMX x
110 AWF x
111 AWR x
112 AXF x
113 AXR x
114 AYF x
115 AYR x
116 CLR x x x
117 CTV x x x
118 LWD x x x
119 NLV x x x
120 PAI x x x
121 TVL x x x
122 WBA x
123 WBC x
124 WBD x
125 WBS x
126 WBT x
127 When filled arrows are used, colors associated with the
129 threshold levels may be applied to either or both the fill or
130 the outline of the arrow. When fill is drawn over the outline
131 (AFO set to 1), LWD should be set to a value greater than 1.0 in
132 order for the outline to be fully visible. The default value of
133 AST is 0.
134 AWF - Arrow Width Fractional Minimum - Real
136 AWF specifies the width of a filled arrow drawn at the minimum
137 length, as a fraction of the width of an arrow drawn at the
138 reference length. If AWF has the value 0.0, then the ratio of
139 the arrow width to the arrow length will be constant for all
140 arrows in the plot. If given the value 1.0, the width will
141 itself be constant for all arrows in the plot, regardless of
142 length. See VFR for a discussion of how the minimum length is
143 determined. AWF has an effect only when AST is set to 1. AWF is
144 allowed to vary between 0.0 and 1.0 and its default value is
145 0.0.
146 AWR - Arrow Width Reference Fraction - Real
148 AWR specifies the width of a filled vector arrow drawn at the
149 reference length, as a fraction of the reference length. See
150 VRL for an explanation of how the reference length is
151 determined. AWR has an effect only when AST is set to 1. AWR is
152 allowed to vary between 0.0 and 1.0 and its default value is
153 0.03.
154 AXF - Arrow X-Coord Fractional Minimum - Real
156 AXF specifies the X component of the head of a filled vector
157 arrow drawn at the minimum length, as a fraction of the X
158 component of the head of an arrow drawn at the reference length.
159 The X component of the arrowhead is the distance from the point
160 of the arrowhead to a point along the centerline of the arrow
161 perpendicular the arrowhead´s rear tips. If AXF has the value
162 0.0, then the ratio of the X component of the arrowhead size to
163 the arrow length will be constant for all vectors in the plot.
164 If given the value 1.0, the arrowhead X component will itself be
165 constant for all arrows in the plot, regardless of their length.
166 See VRL for an explanation of how the reference length is
167 determined. AXF has an effect only when AST is set to 1. AXF is
168 allowed to vary between 0.0 and 1.0 and its default value is
169 0.0.
170 AXR - Arrow X-Coord Reference Fraction - Real
172 AXR specifies the X component of the head of a filled vector
173 arrow drawn at the reference length, as a fraction of reference
174 length. The X component of the arrowhead is the distance from
175 the point of the arrowhead to a point along the centerline of
176 the arrow perpendicular the arrowhead´s rear tips. See VRL for
177 an explanation of how the reference length is determined. AXR
178 has an effect only when AST is set to 1. AXR is allowed to vary
179 between 0.0 and 2.0 and its default value is 0.36.
180 AYF - Arrow Y-Coord Fractional Minimum - Real
182 The value of this parameter, when added to the minimum width
183 value, specifies the Y component length of the arrowhead size
184 for a filled arrow drawn at the minimum length, as a fraction of
185 the length specified by AYF. If given the value 1.0, the
186 arrowhead Y component will extend the same distance
187 perpendicularly from the edge of all arrows in the plot,
188 regardless of their length and width. This can be a useful
189 resource to adjust to ensure that the points of even very short
190 vector arrows remain visible. See VFR for a discussion of how
191 the minimum length is determined. AYF has an effect only when
192 AST is set to 1. AYF is allowed to vary between 0.0 and 1.0 and
193 its default value is 0.25.
194 AYR - Arrow Y-Coord Reference Fraction - Real
196 AYR specifies the perpendicular distance from one side of a
197 filled vector arrowdrawn at the reference length to one of the
198 back tips of the arrowhead. The value represents a fraction of
199 the value of of the reference length and, when added to half the
200 arrow width, determines the Y component of the arrowhead size.
201 See VRL for an explanation of how the reference length is
202 determined. AYR has an effect only when AST is set to 1. AYR
203 is allowed to vary between 0.0 and 1.0 and its default value is
204 0.12.
205 CLR - Array of GKS Color Indices - Integer Array
207 This parameter represents an array containing the GKS color
208 index to use for coloring the vector when the scalar quantity is
209 less than or equal to the threshold value with the same index in
210 the TVL threshold value array. Depending on the settings of AST
211 and ACM it may specify a set of fill color indexes, a set of
212 line color indexes, or both. In order to access a particular
213 element of the CLR array, you must first set the value of PAI,
214 the parameter array index parameter, to the value of the array
215 element´s index. All elements of the array are set to one
216 initially. Note that the Vectors utility makes no calls to set
217 the GKS color representation (GSCR), nor ever modifies the
218 contents of the CLR array; therefore you are responsible for
219 creating a suitably graduated color palette and assigning the
220 color index values into the CLR array, prior to calling VVECTR.
221 Typically, assuming the desired RGB values have been previously
222 stored in a 2 dimensional 3 x n array called RGB, you loop
223 through the calls that set up the color representation and color
224 index as in the following example for a fourteen color palette:
225 DO 100 I=1,14,1
227 CALL GSCR (1,I,RGB(1,I),RGB(2,I),RGB(3,I))
228 CALL VVSETI(´PAI -- Parameter Array Index´, I)
229 CALL VVSETI(´CLR -- GKS Color Index´, I)
230 100 CONTINUE
231 See the descriptions of CTV, NLV, and TVL for details on
233 configuring the vector coloring scheme.
234 CPM - Compatibility Mode - Integer
236 Controls the degree of compatibility between pre-Version 3.2
237 capabilities of the Vectors utility and later versions. You can
238 independently control three behaviors using the nine settings
239 provided:
240 · use of VELVCT and VELVEC input parameters
242 · use of variables initialized in the VELDAT block data
244 statement
245 · use of the old mapping routines, FX, FY, MXF, and MYF.
247 Note, however, that when using the Version 3.2 entry points
249 VVINIT and VVECTR, only the third behavior option has any
250 meaning.
251 When CPM is set to 0, its default value, the Vectors utility´s
253 behavior varies depending on whether you access it through one
254 of the pre-Version 3.2 entry points (VELVCT, VELVEC, and EZVEC),
255 or through the VVINIT/VVECTR interface. Otherwise, positive
256 values result in invocation of the pre-Version 3.2 mapping
257 routines (FX, FY, MXF, and MYF) for the conversion from data to
258 user coordinates. Negative values cause VVMPXY or perhaps VVUMXY
259 to be used instead. When using the pre-Version 3.2 interface,
260 odd values of CPM cause the data values in the VELDAT block data
261 subroutine to override corresponding values initialized in the
262 Version 3.2 VVDATA block data subroutine, or set by the user
263 calling VVSETx routines. Values of CPM with absolute value
264 greater than two cause some of the input arguments to VELVEC and
265 VELVCT to be ignored. These include FLO, HI, NSET, ISPV, SPV and
266 (for VELVCT only) LENGTH.
267 Here is a table of the nine settings of CPM and their effect on
269 the operation of the Vectors utility:
270 Value Use FX, FY, etc. Use VELDAT data Use input args
273 ----- ---------------- --------------- --------------
274 -4 no no no
275 -3 no yes no
276 -2 no no yes
277 -1 no yes yes
278 0 old - yes; new - no (*) yes yes
279 1 yes yes yes
280 2 yes no yes
281 3 yes yes no
282 4 yes no no
283 (*) Old means EZVEC, VELVEC, VELVCT entry point; new,
285 VVINIT/VVECTR. Only the first column applies to the
286 VVINIT/VVECTR interface. See the velvct man page for more
287 detailed emulation information.
288 CTV - Color Threshold Value Control - Integer
290 In conjunction with NLV, this parameter controls vector coloring
291 and the setting of threshold values. The vectors may be colored
292 based on on the vector magnitude or on the contents of a scalar
293 array (VVINIT/VVECTR input argument, P). A table of supported
294 options follows:
295 Value Action
297 -2 Color vector arrows based on scalar array data
299 values; the user is responsible for setting up
300 threshold level array, TVL
301 -1 Color vector arrows based on vector magnitude;
303 the user is responsible for setting up values of
304 threshold level array.
305 0(default) Color all vectors according to the current GKS
307 polyline color index value. Threshold level
308 array, TVL and GKS color index array, CLR are not
309 used.
310 1 Color vector arrows based on vector magnitude;
312 VVINIT assigns values to the first NLV elements
313 of the threshold level array, TVL.
314 2 Color vector arrows based on scalar array data
316 values; VVINIT assigns values to the first NLV
317 elements of the threshold level array, TVL.
318 If you make CTV positive, you must initialize Vectors with a
320 call to VVINIT after the modification.
321 DMN - NDC Minimum Vector Size - Real, Read-Only
323 This parameter is read-only and has a useful value only
324 following a call to VVECTR (directly or through the
325 compatibility version of VELVCT). You may retrieve it in order
326 to determine the length in NDC space of the smallest vector
327 actually drawn (in other words, the smallest vector within the
328 boundary of the user coordinate space that is greater than or
329 equal in magnitude to the value of the VLC parameter). It is
330 initially set to a value of 0.0.
331 DMX - NDC Maximum Vector Size - Real, Read-Only
333 Unlike DMN this read-only parameter has a potentially useful
334 value betweens calls to VVINIT and VVECTR. However, the value it
335 reports may be different before and after the call to VVECTR.
336 Before the VVECTR call it contains the length in NDC space that
337 would be used to render the maximum size vector assuming the
338 user-settable parameter, VRL is set to its default value of 0.0.
339 After the VVECTR call it contains the NDC length used to render
340 the largest vector actually drawn (in other words, the largest
341 vector within the boundary of the user coordinate space that is
342 less than or equal in magnitude to the value of the VHC
343 parameter). See the section on the VRL parameter for information
344 on using the value of DMX after the VVINIT call in order to
345 adjust proportionally the lengths of all the vectors in the
346 plot. It is initially set to a value of 0.0.
347 DPF - Vector Label Decimal Point Control Flag - Integer
349 If DPF is set to a non-zero value, and the optional vector
350 magnitude labels are enabled, the magnitude values are scaled to
351 fit in the range 1 to 999. The labels will contain 1 to 3 digits
352 and no decimal point. Otherwise, the labels will consist of a
353 number up to six characters long, including a decimal point. By
354 default DPF is set to the value 1.
355 LBC - Vector Label Color - Integer
357 This parameter specifies the color to use for the optional
358 vector magnitude labels, as follows:
359 Value Action
361 < -1 Draw labels using the current GKS text color
363 index
364 -1 (default) Draw labels using the same color as the
366 corresponding vector arrow
367 >=0 Draw labels using the LBC value as the GKS text
369 color index
370 LBL - Vector Label Flag - Integer
372 If set non-zero, Vectors draws labels representing the vector
373 magnitude next to each arrow in the field plot. The vector
374 labels are primarily intended as a debugging aid, since in order
375 to avoid excessive overlap, you must typically set the label
376 text size too small to be readable without magnification. For
377 this reason, as well as for efficiency, unlike the other
378 graphical text elements supported by the Vectors utility, the
379 vector labels are rendered using low quality text.
380 LBS - Vector Label Character Size - Real
382 This parameter specifies the size of the characters used for the
383 vector magnitude labels as a fraction of the viewport width. The
384 default value is 0.007.
385 LWD - Vector Linewidth - Real
387 LWD controls the linewidth used to draw the lines that form
389 vector arrows and wind barbs. When the arrows are filled (AST is
390 set to 1) LWD controls the width of the arrow's outline. If the
391 fill is drawn over the outline (AFO set to 1) then LWD must be
392 set to a value greater than 1.0 in order for the outline to
393 appear properly. When AST has the value 2, LWD controls the
394 width of the line elements of wind barbs. When AST is set to 0,
395 specifying line-drawn vector arrows, the linewidth applies
396 equally to the body of the vector and the arrowhead. Overly
397 thick lines may cause the arrow heads to appear smudged. This
398 was part of the motivation for developing the option of filled
399 vector arrows. Note that since linewidth in NCAR Graphics is
400 always calculated relative to a unit linewidth that is dependent
401 on the output device, you may need to adjust the linewidth value
402 depending on the intended output device to obtain a pleasing
403 plot. The default is 1.0, specifying a device-dependent minimum
404 linewidth.
405 MAP - Map Transformation Code - Integer
408 MAP defines the transformation between the data and user
409 coordinate space. Three MAP parameter codes are reserved for
410 pre-defined transformations, as follows:
411 Value Mapping transformation
413 0 (default) Identity transformation between data and user
415 coordinates: array indices of U, V, and P are
416 linearly related to data coordinates.
417 1 Ezmap transformation: first dimension indices of
419 U, V, and P are linearly related to longitude;
420 second dimension indices are linearly related to
421 latitude.
422 2 Polar to rectangular transformation: first
424 dimension indices of U, V, and P are linearly
425 related to the radius; second dimension indices
426 are linearly related to the angle in degrees.
427 If MAP has any other value, Vectors invokes the user-modifiable
429 subroutine, VVUMXY, to perform the mapping. The default version
430 of VVUMXY simply performs an identity transformation. Note that,
431 while the Vectors utility does not actually prohibit the
432 practice, the user is advised not to use negative integers for
433 user-defined mappings, since other utilities in the NCAR
434 Graphics toolkit attach a special meaning to negative mapping
435 codes.
436 For all the predefined mappings, the linear relationship between
438 the grid array indices and the data coordinate system is
439 established using the four parameters, XC1, XCM, YC1, and YCN.
440 The X parameters define a mapping for the first and last indices
441 of the first dimension of the data arrays, and the Y parameters
442 do the same for the second dimension. If MAP is set to a value
443 of one, be careful to ensure that the SET parameter is given a
444 value of zero, since the Ezmap routines require a specific user
445 coordinate space for each projection type, and internally call
446 the SET routine to define the user to NDC mapping. Otherwise,
447 you may choose whether or not to issue a SET call prior to
448 calling VVINIT, modifying the value of SET as required. See the
449 description of the parameter, TRT, and the vvumxy man page for
450 more information.
451 MNC - Minimum Vector Text Block Color - Integer
453 MNC specifies the color of the minimum vector graphical text
454 output block as follows:
455 Value Action
457 <-2 Both the vector arrow and the text are colored
459 using the current text color index.
460 -2 If the vectors are colored by magnitude, both the
462 vector arrow and the text use the GKS color index
463 associated with the minimum vector magnitude.
464 Otherwise, the vector arrow uses the current
465 polyline color index and the text uses the
466 current text color index.
467 -1 (default) If the vectors are colored by magnitude, the
469 vector arrow uses the GKS color index associated
470 with the minimum vector magnitude. Otherwise the
471 vector arrow uses the current polyline color
472 index. The text is colored using the current text
473 color index in either case.
474 >= 0 The value of MNC is used as the color index for
476 both the text and the vector arrow
477 See the description of MNT for more information about the
479 minimum vector text block.
480 MNP - Minimum Vector Text Block Positioning Mode - Integer
482 This parameter allows you to justify the minimum vector text
483 block, taken as a single unit, relative to the text block
484 position established by the parameters, MNX and MNY. Nine
485 positioning modes are available, as follows:
486 Mode Justification
488 -4 The lower left corner of the text block is
490 positioned at MNX, MNY.
491 -3 The center of the bottom edge is positioned at
493 MNX, MNY.
494 -2 The lower right corner is positioned at MNX, MNY.
496 -1 The center of the left edge is positioned at MNX,
498 MNY.
499 0 The text block is centered along both axes at
501 MNX, MNY.
502 1 The center of the right edge is positioned at
504 MNX, MNY.
505 2 The top left corner is positioned at MNX, MNY.
507 3 The center of the top edge is positioned at MNX,
509 MNY.
510 4 (default) The top right corner is positioned at MNX, MNY.
512 See the description of MNT for more information about the
514 minimum vector text block.
515 MNS - Minimum Vector Text Block Character Size - Real
517 MNS specifies the size of the characters used in the minimum
518 vector graphics text block as a fraction of the viewport width.
519 See the description of MNT for more information about the
520 minimum vector text block. The default value of MNS is 0.0075.
521 MNT - Minimum Vector Text String - Character* 36
523 The minimum vector graphics text block consists of a user-
524 definable text string centered underneath a horizontal arrow. If
525 the parameter VLC is set negative the arrow is rendered at the
526 size of the reference minimum magnitude vector (which may be
527 smaller than any vector that actually appears in the plot).
528 Otherwise, the arrow is the size of the smallest vector in the
529 plot. Directly above the arrow is a numeric string in
530 exponential format that represents the vector's magnitude.
531 Use MNT to modify the text appearing below the vector in the
533 minimum vector graphics text block. Currently the string length
534 is limited to 36 characters. Set MNT to a single space (´ ´) to
535 remove the text block, including the vector arrow and the
536 numeric magnitude string, from the plot. The default value is
537 ´Minimum Vector´
538 MNX - Minimum Vector Text Block X Coordinate - Real
540 MNX establishes the X coordinate of the minimum vector graphics
541 text block as a fraction of the viewport width. Values less
542 than 0.0 or greater than 1.0 are permissible and respectively
543 represent regions to the left or right of the viewport. The
544 actual position of the block relative to MNX depends on the
545 value assigned to MNP. See the descriptions of MNT and MNP for
546 more information about the minimum vector text block. The
547 default value of MNX is 0.475.
548 MNY - Minimum Vector Text Block Y Coordinate - Real
550 MNY establishes the Y coordinate of the minimum vector graphics
551 text block as a fraction of the viewport height. Values less
552 than 0.0 or greater than 1.0 are permissible and respectively
553 represent regions below or above the viewport. The actual
554 position of the block relative to MNY depends on the value
555 assigned to MNP. See the descriptions of MNT and MNP for more
556 information about the minimum vector text block. The default
557 value of MNY is -0.01.
558 MSK - Mask To Area Map Flag - Integer
560 Use this parameter to control masking of vectors to an existing
561 area map created by routines in the Areas utility. When MSK is
562 greater than 0, masking is enabled and an the area map must be
563 set up prior to the call to VVECTR. The area map array and, in
564 addition, the name of a user-definable masked drawing routine,
565 must be passed as input parameters to VVECTR. Various values of
566 the MSK parameter have the following effects:
567 Value Effect
569 <= 0 (default) No masking of vectors.
571 1 The subroutine ARDRLN is called internally to
573 decompose the vectors into segments contained
574 entirely within a single area. ARDRLN calls the
575 user-definable masked drawing subroutine.
576 >1 Low precision masking. ARGTAI is called
578 internally to get the area identifiers for the
579 vector base position point. Then the user-
580 definable masked drawing subroutine is called to
581 draw the vector. Vectors with nearby base points
582 may encroach into the intended mask area.
583 See the man page vvudmv for further explanation of masked
585 drawing of vectors
586 MXC - Maximum Vector Text Block Color - Integer
588 MXC specifies the color of the maximum vector graphical text
589 output block as follows:
590 Value Action
592 <-2 Both the vector arrow and the text are colored
594 using the current text color index.
595 -2 If the vectors are colored by magnitude, both the
597 vector arrow and the text use the GKS color index
598 associated with the minimum vector magnitude.
599 Otherwise, the vector arrow uses the current
600 polyline color index and the text uses the
601 current text color index.
602 -1 (default) If the vectors are colored by magnitude, the
604 vector arrow uses the GKS color index associated
605 with the minimum vector magnitude. Otherwise the
606 vector arrow uses the current polyline color
607 index. The text is colored using the current text
608 color index in either case.
609 >= 0 The value of MXC is used as the color index for
611 both the text and the vector arrow
612 See the description of MXT for more information about the
614 maximum vector text block.
615 MXP - Maximum Vector Text Block Positioning Mode - Integer
617 This parameter allows you to justify the maximum vector text
618 block, taken as a single unit, relative to the text block
619 position established by the parameters, MXX and MXY. Nine
620 positioning modes are available, as follows:
621 Mode Justification
623 -4 The lower left corner of the text block is
625 positioned at MXX, MXY.
626 -3 The center of the bottom edge is positioned at
628 MXX, MXY.
629 -2 The lower right corner is positioned at MXX, MXY.
631 -1 The center of the left edge is positioned at MXX,
633 MXY.
634 0 The text block is centered along both axes at
636 MXX, MXY.
637 1 The center of the right edge is positioned at
639 MXX, MXY.
640 2 The top left corner is positioned at MXX, MXY.
642 3 The center of the top edge is positioned at MXX,
644 MXY.
645 4 The top right corner is positioned at MXX, MXY.
647 See the description of MXT for more information about the
649 maximum vector text block.
650 MXS - Maximum Vector Text Block Character Size - Real
652 MXS specifies the size of the characters used in the maximum
653 vector graphics text block as a fraction of the viewport width.
654 See the description of MXT for more information about the
655 maximum vector text block. The default value is 0.0075.
656 MXT - Maximum Vector Text String - Character* 36
658 The maximum vector graphics text block consists of a user-
659 definable text string centered underneath a horizontal arrow. If
660 the parameter VHC is set negative the arrow is rendered at the
661 size of the reference maximum magnitude vector (which may be
662 larger than any vector that actually appears in the plot).
663 Otherwise, the arrow is the size of the largest vector in the
664 plot. Directly above the arrow is a numeric string in
665 exponential format that represents the magnitude of this vector.
666 Use MXT to modify the text appearing below the vector in the
668 maximum vector graphics text block. Currently the string length
669 is limited to 36 characters. Set MXT to a single space (´ ´) to
670 completely remove the text block, including the vector arrow and
671 the numeric magnitude string, from the plot. Note that the name
672 "Maximum Vector Text Block" is no longer accurate, since using
673 the parameter VRM it is now possible to establish a reference
674 magnitude that is smaller than the maximum magnitude in the data
675 set. A more accurate name would be "Reference Vector Text
676 Block". The default value of MXT is ´Maximum Vector´.
677 MXX - Maximum Vector Text Block X Coordinate - Real
679 MXX establishes the X coordinate of the maximum vector graphics
680 text block as a fraction of the viewport width. Values less
681 than 0.0 or greater than 1.0 are permissible and respectively
682 represent regions below or above of the viewport. The actual
683 position of the block relative to MXX depends on the value
684 assigned to MXP. See the descriptions of MXT and MXP for more
685 information about the maximum vector text block. The default
686 value is 0.525.
687 MXY - Maximum Vector Text Block Y Coordinate - Real
689 MXY establishes the Y coordinate of the maximum vector graphics
690 text block as a fraction of the viewport width. Values less
691 than 0.0 or greater than 1.0 are permissible and respectively
692 represent regions below or above the viewport. The actual
693 position of the block relative to MXY depends on the value
694 assigned to MXP. See the descriptions of MXT and MXP for more
695 information about the maximum vector text block. The default
696 value is -0.01.
697 NLV - Number of Colors Levels - Integer
699 NLV specifies the number of color levels to use when coloring
700 the vectors according to data in a scalar array or by vector
701 magnitude. Anytime CTV has a non-zero value, you must set up
702 the first NLV elements of the color index array CLR. Give each
703 element the value of a GKS color index that must be defined by a
704 call to the the GKS subroutine, GSCR, prior to calling VVECTR.
705 If CTV is less than 0, in addition to setting up the CLR array,
706 you are also responsible for setting the first NLV elements of
707 the threshold values array, TVL to appropriate values. NLV is
708 constrained to a maximum value of 255. The default value of NLV
709 is 0, specifying that vectors are colored according to the value
710 of the GKS polyline color index currently in effect, regardless
711 of the value of CTV. If CTV is greater than 0, you must
712 initialize Vectors with a call to VVINIT after modifying this
713 parameter.
714 PAI - Parameter Array Index - Integer
716 The value of PAI must be set before calling VVGETC, VVGETI,
717 VVGETR, VVSETC, VVSETI, or VVSETR to access any parameter which
718 is an array; it acts as a subscript to identify the intended
719 array element. For example, to set the 10th color threshold
720 array element to 7, use code like this:
721 CALL VVSETI (´PAI - PARAMETER ARRAY INDEX´,10)
723 CALL VVSETI (´CLR - Color Index´,7)
724 The default value of PAI is one.
726 PLR - Polar Input Mode - Integer
728 When PLR is greater than zero, the vector component arrays are
729 considered to contain the field data in polar coordinate form:
730 the U array is treated as containing the vector magnitude and
731 the V array as containing the vector angle. Be careful not to
732 confuse the PLR parameter with the MAP parameter set to polar
733 coordinate mode (2). The MAP parameter relates to the location
734 of the vector, not its value. Here is a table of values for PLR:
735 Value Meaning
737 0 (default) U and V arrays contain data in cartesian
739 component form.
740 1 U array contains vector magnitudes; V array
742 contains vector angles in degrees.
743 2 U array contain vector magnitudes; V array
745 contains vector angles in radians.
746 You must initialize Vectors with a call to VVINIT after
748 modifying this parameter.
749 PMN - Minimum Scalar Array Value - Real, Read-Only
751 You may retrieve the value specified by PMN at any time after a
752 call to VVINIT. It will contain a copy of the minimum value
753 encountered in the scalar data array. If no scalar data array
754 has been passed into VVINIT it will have a value of 0.0.
755 PMX - Maximum Scalar Array Value - Real
757 You may retrieve the value specified by PMX at any time after a
758 call to VVINIT. It contains a copy of the maximum value
759 encountered in the scalar data array. If no scalar data array
760 has been passed into VVINIT it will have a value of 0.0.
761 PSV - P Array Special Value - Real
763 Use PSV to indicate the special value that flags an unknown data
764 value in the P scalar data array. This value will not be
765 considered in the determination of the data set maximum and
766 minimum values. Also, depending on the setting of the SPC
767 parameter, the vector may be specially colored to flag the
768 unknown data point, or even eliminated from the plot. You must
769 initialize Vectors with a call to VVINIT after modifying this
770 parameter.
771 SET - SET Call Flag - Integer
773 Give SET the value 0 to inhibit the SET call VVINIT performs by
774 default. Arguments 5-8 of a SET call made by the user must be
775 consistent with the ranges of the user coordinates expected by
776 Vectors. This is determined by the mapping from grid to data
777 coordinates as specified by the values of the parameters XC1,
778 XCM, YC1, YCN, and also by the mapping from data to user
779 coordinates established by the MAP parameter. You must
780 initialize Vectors with a call to VVINIT after modifying this
781 parameter. The default value of SET is 1.
782 SPC - Special Color - Integer
784 SPC controls special value processing for the optional scalar
785 data array used to color the vectors, as follows:
786 Value Effect
788 < 0 (default) The P scalar data array is not examined for
790 special values.
791 0 Vectors at P scalar array special value locations
793 are not drawn.
794 > 0 Vectors at P scalar array special value locations
796 are drawn using color index SPC.
797 You must initialize Vectors with a call to VVINIT after
799 modifying this parameter.
800 SVF - Special Value Flag - Integer
802 The special value flag controls special value processing for the
803 U and V vector component data arrays. Special values may appear
804 in either the U or V array or in both of them. Five different
805 options are available (although the usefulness of some of the
806 choices is debatable):
807 Value Effect
809 0 (default) Neither the U nor the V array is examined for
811 special values
812 1 Vectors with special values in the U array are
814 not drawn
815 2 Vectors with special values in the V array are
817 not drawn
818 3 Vectors with special values in either the U or V
820 array are not drawn
821 4 Vectors with special values in both the U and V
823 arrays are not drawn
824 The U and V special values are defined by setting parameters USV
826 and VSV. You must initialize Vectors with a call to VVINIT after
827 modifying this parameter.
828 TRT - Transformation Type - Integer
830 As currently implemented, TRT further qualifies the mapping
831 transformation specified by the MAP parameter, as follows:
832 Value Effect
834 -1 Direction, magnitude, and location are all
836 transformed. This option is not currently
837 supported by any of the pre-defined coordinate
838 system mappings.
839 0 Only location is transformed
841 1 (default) Direction and location are transformed
843 This parameter allows you to distinguish between a system that
845 provides a mapping of location only into an essentially
846 cartesian space, and one in which the space itself mapped. To
847 understand the difference, using polar coordinates as an
848 example, imagine a set of wind speed monitoring units located on
849 a radial grid around some central point such as an airport
850 control tower. Each unit´s position is defined in terms of its
851 distance from the tower and its angular direction from due east.
852 However, the data collected by each monitoring unit is
853 represented as conventional eastward and northward wind
854 components. Assuming the towers´s location is at a moderate
855 latitude, and the monitoring units are reasonably ´local´, this
856 is an example of mapping a radially defined location into a
857 nearly cartesian space (i.e. the eastward components taken alone
858 all point in a single direction on the plot, outlining a series
859 of parallel straight lines). One would set MAP to two (for the
860 polar transformation) and TRT to zero to model this data on a
861 plot generated by the Vectors utility.
862 On the other hand, picture a set of wind data, again given as
864 eastward and northward wind components, but this time the center
865 of the polar map is actually the south pole. In this case, the
866 eastward components do not point in a single direction; instead
867 they outline a series of circles around the pole. This is a
868 space mapping transformation: one would again set MAP to two,
869 but TRT would be set to one to transform both direction and
870 location.
871 Changing the setting of this parameter affects the end results
873 only when a non-uniform non-linear mapping occurs at some point
874 in the transformation pipeline. For this discussion a uniform
875 linear transformation is defined as one which satisfies the
876 following equations:
877 x_out = x_offset + scale_constant * x_in
879 y_out = y_offset + scale_constant * y_in
880 If scale_constant is not the same for both the X axis and the Y
882 axis then the mapping is non-uniform.
883 This option is currently implemented only for the pre-defined
885 MAP parameter codes, 0 and 2, the identity mapping and the polar
886 coordinate mapping. However, it operates on a different stage of
887 the transformation pipeline in each case. The polar mapping is
888 non-linear from data to user coordinates. The identity mapping,
889 even though necessarily linear over the data to user space
890 mapping, can have a non-uniform mapping from user to NDC space,
891 depending on the values given to the input parameters of the SET
892 call. This will be the case whenever the LL input parameter is
893 other than one, or when LL equals one, but the viewport and the
894 user coordinate boundaries do not have the same aspect ratio.
895 Thus for a MAP value of 2, TRT affects the mapping between data
896 and user space, whereas for MAP set to 0, TRT influences the
897 mapping between user and NDC space.
898 TVL - Array of Threshold Values - Real Array
900 TVL is an array of threshold values that is used to determine
901 the individual vector color, when CTV and NLV are both non-zero.
902 For each vector the TVL array is searched for the smallest value
903 greater than or equal to the scalar value associated with the
904 vector. The array subscript of this element is used as an index
905 into the CLR array. Vectors uses the GKS color index found at
906 this element of the CLR array to set the color for the vector.
907 Note that Vectors assumes that the threshold values are
908 monotonically increasing.
909 When CTV is less than 0, you are responsible for assigning
911 values to the elements of TVL yourself. To do this, first set
912 the PAI parameter to the index of the threshold level element
913 you want to define, then call VVSETR to set TVL to the
914 appropriate threshold value for this element. Assuming the
915 desired values have previously been stored in a array named
916 TVALS, you could assign the threshold values for a fourteen
917 level color palette using the following loop:
918 DO 100 I=1,14,1
920 CALL VVSETI(PAI -- Parameter Array Index, I)
921 CALL VVSETR(TVL -- Threshold Value, TVALS(I))
922 100 CONTINUE
923 When CTV is greater than 0, Vectors assigns values into TVL
925 itself. Each succeeding element value is greater than the
926 preceding value by the value of the expression:
927 (maximum_data_value - minimum_data_value) / NLV
929 where the data values are either from the scalar data array or
931 are the magnitudes of the vectors in the vector component
932 arrays. The first value is equal to the minimum value plus the
933 expression; the final value (indexed by the value of NLV) is
934 equal to the maximum value. If Vectors encounters a value
935 greater than the maximum value in the TVL array while processing
936 the field data, it gives the affected vector the color
937 associated with the maximum TVL value.
938 USV - U Array Special Value - Real
940 USV is the U vector component array special value. It is a value
941 outside the range of the normal data used to indicate that there
942 is no valid data for this grid location. When SVF is set to 1 or
943 3, Vectors will not draw a vector whose U component has the
944 special value. You must initialize Vectors with a call to VVINIT
945 after modifying this parameter. It has a default value of 1.0
946 E12.
947 VFR - Minimum Vector Fractional Length - Real
949 Use this parameter to adjust the realized size of the reference
950 minimum magnitude vector relative to the reference maximum
951 magnitude vector in order to improve the appearance or perhaps
952 the information content of the plot. Specify VFR as a value
953 between 0.0 and 1.0, where 0.0 represents an unmodified linear
954 scaling of the realized vector length, in proportion to
955 magnitude, and 1.0 specifies that the smallest vector be
956 represented at 1.0 times the length of the largest vector,
957 resulting in all vectors, regardless of magnitude, having the
958 same length on the plot. A value of 0.5 means that the smallest
959 magnitude vector appears half as long as the largest magnitude
960 vector; intermediate sizes are proportionally scaled to lengths
961 between these extremes. Where there is a wide variation in
962 magnitude within the vector field, you can use this parameter to
963 increase the size of the smallest vectors to a usefully visible
964 level. Where the variation is small, you can use the parameter
965 to exaggerate the differences that do exist. See also the
966 descriptions of VRL, VLC, VHC, and VRM. The default value is
967 0.0.
968 VHC - Vector High Cutoff Value - Real
970 If the parameter VRM is set to a value greater than 0.0, it
971 supercedes the use of VHC to specify the reference magnitude.
972 VRM allows greater flexibility in that it can be used to specify
973 an arbitrary reference magnitude that need not be the maximum
974 magnitude contained in the data set. VHC can still be used to
975 set a high cutoff value -- no vectors with magnitude greater
976 than the cutoff value will be displayed in the plot.
977 If VRM has its default value, 0.0, VHC specifies the reference
979 maximum magnitude represented by an arrow of length VRL (as a
980 fraction of the viewport width). The realized length of each
981 individual vector in the plot is based on its magnitude relative
982 to the reference maximum magnitude and, if VFR is non-zero, the
983 reference minimum magnitude (as specified by VLC). Note that the
984 reference maximum magnitude may be greater than the magnitude of
985 any vector in the dataset. The effect of this parameter varies
986 depending on its value, as follows:
987 Value Effect
989 < 0.0 The absolute value of VHC unconditionally
991 determines the reference maximum magnitude.
992 Vectors in the dataset with magnitude greater
993 than VHC are not displayed.
994 0.0 (default) The vector with the greatest magnitude in the
996 dataset determines the reference maximum
997 magnitude.
998 > 0.0 The minimum of VHC and the vector with the
1000 greatest magnitude in the data set determines the
1001 reference maximum magnitude. Vectors in the
1002 dataset with magnitude greater than VHC are not
1003 displayed.
1004 Typically, for direct comparison of the output of a series of
1006 plots, you would set VHC to a negative number, the absolute
1007 value of which is greater than any expected vector magnitude in
1008 the series. You can turn on Vectors statistics reporting using
1009 the parameter VST in order to see if any vectors in the datasets
1010 do exceed the maximum magnitude you have specified. See also the
1011 descriptions of the parameters VRM, VRL, DMX, VLC, and VFR.
1012 VLC - Vector Low Cutoff Value - Real
1014 Use this parameter to prevent vectors smaller than the specified
1015 magnitude from appearing in the output plot. VLC also specifies
1016 the reference minimum magnitude that is rendered at the size
1017 specified by the product of VRL and VFR (as a fraction of the
1018 viewport width), when VFR is greater than 0.0. Note that the
1019 reference minimum magnitude may be smaller than the magnitude of
1020 any vector in the dataset. The effect of this parameter varies
1021 depending on its value, as follows:
1022 Value Effect
1024 < 0.0 The absolute value of VLC unconditionally
1026 determines the reference minimum magnitude.
1027 Vectors in the dataset with magnitude less than
1028 VLC do not appear.
1029 0.0 (default) The vector with the minimum magnitude in the
1031 dataset determines the reference minimum
1032 magnitude.
1033 > 0.0 The maximum of VLC and the vector with the least
1035 magnitude in the data set determines the
1036 reference minimum magnitude. Vectors in the
1037 dataset with magnitude less than VLC do not
1038 appear.
1039 The initialization subroutine, VVINIT, calculates the magnitude
1041 of all the vectors in the vector field, and stores the maximum
1042 and minimum values. You may access these values by retrieving
1043 the read-only parameters, VMX and VMN. Thus it is possible to
1044 remove the small vectors without prior knowledge of the data
1045 domain. The following code fragment illustrates how the smallest
1046 10% of the vectors could be removed:
1047 CALL VVINIT(...
1049 CALL VVGETR(´VMX - Vector Maximum Magnitude´, VMX)
1050 CALL VVGETR(´VMN - Vector Minimum Magnitude´, VMN)
1051 CALL VVSETR(´VLC - Vector Low Cutoff Value´,
1052 + VMN+0.1*(VMX-VMN))
1053 CALL VVECTR(...
1054 On the other hand, when creating a series of plots that you
1057 would like to compare directly and you are using VFR to set a
1058 minimum realized size for the vectors, you can ensure that all
1059 vectors of a particular length represent the same magnitude on
1060 all the plots by setting both VHC and VLC to negative values. If
1061 you do not actually want to remove any vectors from the plot,
1062 make VLC smaller in absolute value than any expected magnitude.
1063 You can turn on Vectors statistics reporting using the parameter
1064 VST in order to see if any vectors in the datasets are less the
1065 minimum magnitude you have specified. See also the descriptions
1066 of parameters VFR, VRL, VHC, DMN, and VRM.
1067 VMD - Vector Minimum Distance - Real
1069 If VMD is set to a value greater than 0.0, it specifies, as a
1070 fraction of the viewport width, a minimum distance between
1071 adjacent vectors arrows in the plot. The distribution of vectors
1072 is analyzed and then vectors are selectively removed in order to
1073 ensure that the remaining vectors are separated by at least the
1074 specified distance. The thinning algorithm requires that you
1075 supply Vectors with a work array twice the size of the VVINIT
1076 arguments N and M multiplied together. Use of this capability
1077 adds some processing time to the execution of Vectors. If VMD is
1078 set to a value greater than 0.0 and no work array is provided,
1079 an error condition results.
1080 If the data grid is transformed in such a way that adjacent grid
1082 cells become very close in NDC space, as for instance in many
1083 map projections near the poles, you can use this parameter to
1084 reduce the otherwise cluttered appearance of these regions of
1085 the plot. The default value of VMD is 0.0.
1086 VMN - Minimum Vector Magnitude - Real, Read-Only
1088 After a call to VVINIT, VMN contains the value of the minimum
1089 vector magnitude in the U and V vector component arrays. Later,
1090 after VVECTR is called, it is modified to contain the magnitude
1091 of the smallest vector actually displayed in the plot. This is
1092 the vector with the smallest magnitude greater than or equal to
1093 the value specified by VLC, the vector low cutoff parameter,
1094 (0.0 if VLC has its default value) that falls within the user
1095 coordinate window boundaries. The value contained in VMN is the
1096 same as that reported as the 'Minimum plotted vector magnitude'
1097 when Vectors statistics reporting is enabled. It may be larger
1098 than the reference minimum magnitude reported by the minimum
1099 vector text block if you specify the VLC parameter as a negative
1100 value. VMN is initially set to a value of 0.0.
1101 VMX - Maximum Vector Magnitude - Real, Read-Only
1103 After a call to VVINIT, VMX contains the value of the maximum
1104 vector magnitude in the U and V vector component arrays. Later,
1105 after VVECTR is called, it is modified to contain the magnitude
1106 of the largest vector actually displayed in the plot. This is
1107 the vector with the largest magnitude less than or equal to the
1108 value specified by VHC, the vector high cutoff parameter, (the
1109 largest floating point value available on the machine if VHC has
1110 its default value, 0.0) that falls within the user coordinate
1111 window boundaries. The value contained in VMX is the same as
1112 that reported as the 'Maximum plotted vector magnitude' when
1113 Vectors statistics reporting is enabled. It may be smaller than
1114 the reference maximum magnitude reported by the maximum vector
1115 text block if you specify the VHC parameter as a negative value.
1116 VMX is initially set to a value of 0.0.
1117 VPB - Viewport Bottom - Real
1119 The parameter VPB has an effect only when SET is non-zero,
1120 specifying that Vectors should do the call to SET. It specifies
1121 a minimum boundary value for the bottom edge of the viewport in
1122 NDC space, and is constrained to a value between 0.0 and 1.0. It
1123 must be less than the value of the Viewport Top parameter, VPT.
1124 The actual value of the viewport bottom edge used in the plot
1125 may be greater than the value of VPB, depending on the setting
1126 of the Viewport Shape parameter, VPS. You must initialize
1127 Vectors with a call to VVINIT after modifying this parameter.
1128 The default value of VPB is 0.05.
1129 VPL - Viewport Left - Real
1131 The parameter VPL has an effect only when SET is non-zero,
1132 specifying that Vectors should do the call to SET. It specifies
1133 a minimum boundary value for the left edge of the viewport in
1134 NDC space, and is constrained to a value between 0.0 and 1.0. It
1135 must be less than the value of the Viewport Right parameter,
1136 VPR. The actual value of the viewport left edge used in the plot
1137 may be greater than the value of VPL, depending on the setting
1138 of the Viewport Shape parameter, VPS. You must initialize
1139 Vectors with a call to VVINIT after modifying this parameter.
1140 The default value of VPL is 0.05.
1141 VPO - Vector Positioning Mode - Integer
1143 VPO specifies the position of the vector arrow in relation to
1144 the grid point location of the vector component data. Three
1145 settings are available, as follows:
1146 Value Effect
1148 <0 The head of the vector arrow is placed at the
1150 grid point location
1151 0 (default) The center of the vector arrow is placed at the
1153 grid point location
1154 >0 The tail of the vector arrow is placed at the
1156 grid point location
1157 VPR - Viewport Right - Real
1159 The parameter VPR has an effect only when SET is non-zero,
1160 specifying that Vectors should do the call to SET. It specifies
1161 a maximum boundary value for the right edge of the viewport in
1162 NDC space, and is constrained to a value between 0.0 and 1.0. It
1163 must be greater than the value of the Viewport Left parameter,
1164 VPL. The actual value of the viewport right edge used in the
1165 plot may be less than the value of VPR, depending on the setting
1166 of the Viewport Shape parameter, VPS. You must initialize
1167 Vectors with a call to VVINIT after modifying this parameter.
1168 The default value of VPR is 0.95.
1169 VPS - Viewport Shape - Real
1171 The parameter VPS has an effect only when SET is non-zero,
1172 specifying that Vectors should do the call to SET; it specifies
1173 the desired viewport shape, as follows:
1174 Value Effect
1176 <0.0 The absolute value of VPS specifies the shape to
1178 use for the viewport., as the ratio of the
1179 viewport width to its height,
1180 0.0 The viewport completely fills the area defined by
1182 the boundaries specifiers, VPL, VPR, VPB, VPT
1183 >0.0,<1.0 (0.25, default)
1185 Use R = (XCM-XC1)/(YCN-YC1) as the viewport shape
1186 if MIN(R, 1.0/R) is greater than VPS. Otherwise
1187 determine the shape as when VPS is equal to 0.0.
1188 >= 1.0 Use R = (XCM-XC1)/(YCN-YC1) as the viewport shape
1190 if MAX(R, 1.0/R) is less than VPS. Otherwise make
1191 the viewport a square.
1192 The viewport, whatever its final shape, is centered in, and made
1194 as large as possible in, the area specified by the parameters
1195 VPB, VPL, VPR, and VPT. You must initialize Vectors with a call
1196 to VVINIT after modifying this parameter. The default value of
1197 VPS is 25.
1198 VPT - Viewport Top - Real
1200 The parameter VPT has an effect only when SET is non-zero,
1201 specifying that Vectors should do the call to SET. It specifies
1202 a maximum boundary value for the top edge of the viewport in NDC
1203 space, and is constrained to a value between 0.0 and 1.0. It
1204 must be greater than the value of the Viewport Bottom parameter,
1205 VPB. The actual value of the viewport top edge used in the plot
1206 may be less than the value of VPT, depending on the setting of
1207 the Viewport Shape parameter, VPS. You must initialize Vectors
1208 with a call to VVINIT after modifying this parameter. The
1209 default value of VPT is 0.95.
1210 VRL - Vector Reference Length - Real
1212 Use this parameter to specify the realized length of the
1213 reference magnitude vector as a fraction of the viewport width.
1214 Based on this value a reference length in NDC units is
1215 established, from which the length of all vectors in the plot is
1216 derived. The relationship between magnitude and length also
1217 depends on the setting of the minimum vector magnitude fraction
1218 parameter, VFR, but, given the default value of VFR (0.0), the
1219 length of each vector is simply proportional to its relative
1220 magnitude. Note that the arrow size parameters, AMN and AMX,
1221 allow independent control over the minimum and maximum size of
1222 the vector arrowheads.
1223 Given a reference length, Vectors calculates a maximum length
1225 based on the ratio of the reference magnitude to the larger of
1226 the maximum magnitude in the data set and the reference
1227 magnitude itself. This length is accessible in units of NDC via
1228 the read-only parameter, DMX. If VRL is set less than or equal
1229 to 0.0, VVINIT calculates a default value for DMX, based on the
1230 size of a grid box assuming a linear mapping from grid
1231 coordinates to NDC space. The value chosen is one half the
1232 diagonal length of a grid box. By retrieving the value of DMX
1233 and calling GETSET to retrieve the viewport boundaries after the
1234 call to VVINIT, you can make relative adjustments to the vector
1235 length, as shown by the following example, where the maximum
1236 vector length is set to 1.5 times its default value:
1237 CALL VVINIT(...
1239 CALL VVGETR(´DMX - NDC Maximum Vector Size´, DMX)
1240 CALL GETSET(VL,VR,VB,VT,UL,UR,UB,UT,LL)
1241 VRL = 1.5 * DMX / (VR - VL)
1242 CALL VVSETR(´VRL - Vector Realized Length´, VRL)
1243 CALL VVECTR(...
1244 When VVECTR sees that VRL is greater than 0.0, it will calculate
1246 a new value for DMX. If VRL is never set, the initially
1247 calculated value of DMX is used as the reference length. Do not
1248 rely on the internal parameters used for setting the viewport,
1249 VPL, VPR, VPB and VPT to retrieve information about viewport in
1250 lieu of using the GETSET call. These values are ignored entirely
1251 if the SET parameter is zero, and even if used, the viewport may
1252 be adjusted from the specified values depending on the setting
1253 of the viewport shape parameter, VPS. See also the descriptions
1254 of VFR, VRM, and VHC. The default value of VRL is 0.0.
1255 VRM - Vector Reference Magnitude - Real
1257 The introduction of the parameter VRM means that it is now
1258 possible to specify an arbitrary vector magnitude as the
1259 reference magnitude appearing in the "Maximum Vector Text Block"
1260 annotation. The reference magnitude no longer needs to be
1261 greater or equal to the largest magnitude in the data set. When
1262 VRM has a value greater than 0.0, it specifies the magnitude of
1263 the vector arrow drawn at the reference length. See VRL for an
1264 explanation of how the reference length is determined. If VRM is
1265 less than or equal to 0.0, the reference magnitude is determined
1266 by the value of VHC, the vector high cutoff value. If, in turn,
1267 VHC is equal to 0.0 the maximum magnitude in the vector field
1268 data set becomes the reference magnitude. The default value of
1269 VRM is 0.0.
1270 VST - Vector Statistics Output Flag - Integer
1272 If VST is set to one, VVECTR writes a summary of its operation
1273 to the default logical output unit, including the number of
1274 vectors plotted, number of vectors rejected, minimum and maximum
1275 vector magnitudes, and if coloring the vectors according to data
1276 in the scalar array, the maximum and minimum scalar array values
1277 encountered. Here is a sample of the output:
1278 VVECTR Statistics
1280 Vectors plotted: 906
1281 Vectors rejected by mapping routine: 0
1282 Vectors under minimum magnitude: 121
1283 Vectors over maximum magnitude: 0
1284 Other zero length vectors: 0
1285 Rejected special values: 62
1286 Minimum plotted vector magnitude: 9.94109E-02
1287 Maximum plotted vector magnitude: 1.96367
1288 Minimum scalar value: -1.00000
1289 Maximum scalar value: 1.00000
1290 VSV - V Array Special Value - Real
1292 VSV is the V vector component array special value. It is a value
1293 outside the range of the normal data used to indicate that there
1294 is no valid data for this grid location. When SVF is set to 2 or
1295 3, Vectors will not draw a vector whose V component has the
1296 special value. You must initialize Vectors with a call to VVINIT
1297 after modifying this parameter. It has a default value of 1.0
1298 E12.
1299 WBA - Wind Barb Angle - Real
1302 WBA sets the angle of the wind barb ticks in degrees as measured
1304 clockwise from the vector direction. It also sets the angle
1305 between the hypotenuse of the triangle defining the pennant
1306 polygon and the vector direction. You can render southern
1307 hemisphere wind barbs, which by convention, have their ticks and
1308 pennants on the other side of the shaft, by setting WBA to a
1309 negative value. WBA has an effect only when AST has the value 2.
1310 WBC - Wind Barb Calm Circle Size - Real
1313 WBC sets the diameter of the circle used to represent small
1315 vector magnitudes (less than 2.5) as a fraction of the overall
1316 wind barb length (the value of the VRL parameter). WBC has an
1317 effect only when AST has the value 2.
1318 WBD - Wind Barb Distance Between Ticks - Real
1321 WBD sets the distance between adjacent wind barbs ticks along
1323 the wind barb shaft as a fraction of the overall wind barb
1324 length (the value of the VRL parameter). Half this distance is
1325 used as the spacing between adjacent wind barb pennants. Note
1326 that there is nothing to to prevent ticks and/or pennants from
1327 continuing off the end of the shaft if a vector of high enough
1328 magnitude is encountered. You are responsible for adjusting the
1329 parameters appropriately for the range of magnitudes you need to
1330 handle. WBD has an effect only when AST has the value 2.
1331 WBS - Wind Barb Scale Factor - Real
1334 WBS specifies a factor by which magnitudes passed to the wind
1336 barb drawing routines are to be scaled. It can be used to
1337 convert vector data given in other units into the conventional
1338 units used with wind barbs, which is knots. For instance, if the
1339 data are in meters per second, you could set WBS to 1.8974 to
1340 create a plot with conventional knot-based wind barbs. Note that
1341 setting WBS does not currently have any effect on the magnitude
1342 values written into the maximum or minimum vector legends. WBS
1343 has an effect only when AST has the value 2.
1344 WBT - Wind Barb Tick Size - Real
1347 WBT the length of the wind barb ticks as a fraction of the
1349 overall length of a wind barb (the value of the VRL parameter).
1350 The wind barb length is defined as the length of the wind barb
1351 shaft plus the projection of a full wind barb tick along the
1352 axis of the shaft. Therefore, increasing the value of WBT, for a
1353 given value of VRL has the effect of reducing the length of the
1354 shaft itself somewhat. You may need to increase VRL itself to
1355 compensate. WBT also sets the hypotenuse length of the triangle
1356 defining the pennant polygon. WBT has an effect only when AST
1357 has the value 2.
1358 WDB - Window Bottom - Real
1361 When VVINIT does the call to SET, the parameter WDB is used to
1362 determine argument number 7, the user Y coordinate at the bottom
1363 of the window. If WDB is not equal to WDT, WDB is used. If WDB
1364 is equal to WDT, but YC1 is not equal to YCN, then YC1 is used.
1365 Otherwise, the value 1.0 is used. You must initialize Vectors
1366 with a call to VVINIT after modifying this parameter. The
1367 default value of WDB is 0.0.
1368 WDL - Window Left - Real
1370 When VVINIT the call to SET, the parameter WDL is used to
1371 determine argument number 5, the user X coordinate at the left
1372 edge of the window. If WDL is not equal to WDR, WDL is used. If
1373 WDL is equal to WDR, but XC1 is not equal to XCM, then XC1 is
1374 used. Otherwise, the value 1.0 is used. You must initialize
1375 Vectors with a call to VVINIT after modifying this parameter.
1376 The default value of WDL is 0.0.
1377 WDR - Window Right - Real
1379 When VVINIT does the call to SET, the parameter WDR is used to
1380 determine argument number 6, the user X coordinate at the right
1381 edge of the window. If WDR is not equal to WDL, WDR is used. If
1382 WDR is equal to WDL, but XCM is not equal to XC1, then XCM is
1383 used. Otherwise, the value of the VVINIT input parameter, M,
1384 converted to a real, is used. You must initialize Vectors with a
1385 call to VVINIT after modifying this parameter. The default value
1386 of WDR is 0.0.
1387 WDT - Window Top - Real
1389 When VVINIT does the call to SET, the parameter WDB is used to
1390 determine argument number 8, the user Y coordinate at the top of
1391 the window. If WDT is not equal to WDB, WDT is used. If WDT is
1392 equal to WDB, but YCN is not equal to YC1 then YCN is used.
1393 Otherwise, the value of the VVINIT input parameter, N, converted
1394 to a real, is used. You must initialize Vectors with a call to
1395 VVINIT after modifying this parameter. The default value of WDT
1396 is 0.0.
1397 XC1 - X Coordinate at Index 1 - Real
1399 The parameter XC1 specifies the X coordinate value that
1400 corresponds to a value of 1 for the first subscript of the U, V,
1401 vector component arrays as well as for the P scalar data array,
1402 if used. Together with XCM, YC1, and YCN it establishes the
1403 mapping from grid coordinate space to data coordinate space. If
1404 XC1 is equal to XCM, 1.0 will be used. You must initialize
1405 Vectors with a call to VVINIT after modifying this parameter.
1406 The default value of XC1 is 0.0.
1407 XCM - X Coordinate at Index M - Real
1409 The parameter XCM specifies the X coordinate value that
1410 corresponds to the value of the VVINIT input parameter, M, for
1411 the first subscript of the U and V vector component arrays as
1412 well as for the P scalar data array, if used. Together with
1413 XC1, YC1, and YCN it establishes the mapping from grid
1414 coordinate space to data coordinate space. If XC1 is equal to
1415 XCM, the value of M, converted to a real, will be used. You must
1416 initialize Vectors with a call to VVINIT after modifying this
1417 parameter. The default value of XCM is 0.0.
1418 XIN - X Axis Array Increment (Grid) - Integer
1420 XIN controls the step size through first dimensional subscripts
1421 of the U,V vector component arrays and also through the P scalar
1422 data array if it is used. For dense arrays plotted at a small
1423 scale, you could set this parameter to a value greater than one
1424 to reduce the crowding of the vectors and hopefully improve the
1425 intelligibility of the plot. The grid point with subscripts
1426 (1,1) is always included in the plot, so if XIN has a value of
1427 three, for example, only grid points with first dimension
1428 subscripts 1, 4, 7... (and so on) will be plotted. See also YIN.
1429 You must initialize Vectors with a call to VVINIT after
1430 modifying this parameter. The default value of XIN is 1.
1431 YC1 - Y Coordinate at Index 1 - Real
1433 The parameter YC1 specifies the Y coordinate value that
1434 corresponds to a value of 1 for the first subscript of the U, V,
1435 vector component arrays as well as for the P scalar data array,
1436 if used. Together with YCN, XC1, and XCM it establishes the
1437 mapping from grid coordinate space to data coordinate space. If
1438 YC1 is equal to YCN, 1.0 will be used. You must initialize
1439 Vectors with a call to VVINIT after modifying this parameter.
1440 The default value of YC1 is 0.0.
1441 YCN - Y Coordinate at Index N - Real
1443 The parameter YCN specifies the Y coordinate value that
1444 corresponds to the value of the VVINIT input parameter, N, for
1445 the second subscript of the U and V vector component arrays as
1446 well as the P scalar data array, if used. Together with YC1,
1447 XC1, and XCM it establishes the mapping from grid coordinate
1448 space to data coordinate space. If YC1 is equal to YCN, the
1449 value of N, converted to a real, will be used. You must
1450 initialize Vectors with a call to VVINIT after modifying this
1451 parameter. The default value of YCN is 0.0.
1452 YIN - Y Axis Array Increment (Grid) - Integer
1454 YIN controls the step size through the second dimension
1455 subscripts of the U and V vector component arrays and also
1456 through the P scalar data array if it is used. For dense arrays
1457 plotted at a small scale, you could set this parameter to a
1458 value greater than one to reduce the crowding of the vectors and
1459 hopefully improve the intelligibility of the plot. The grid
1460 point with subscripts (1,1) is always included in the plot, so
1461 if YIN has a value of three, for example, only grid points with
1462 second dimension subscripts 1, 4, 7... (and so on) will be
1463 plotted. See also XIN. You must initialize Vectors with a call
1464 to VVINIT after modifying this parameter. The default value of
1465 YIN is 1.
1466 ZFC - Zero Field Text Block Color - Integer
1468 If ZFC is greater or equal to zero, it specifies the GKS color
1469 index to use to color the Zero Field text block. Otherwise the
1470 Zero Field text block is colored using the current GKS text
1471 color index. The default value of ZFC is -1.
1472 ZFP - Zero Field Text Block Positioning Mode - Integer
1474 The ZFP parameter allows you to justify, using any of the 9
1475 standard justification modes, the Zero Field text block unit
1476 with respect to the position established by the parameters, ZFX
1477 and ZFY The position modes are supported as follows:
1478 Mode Justification
1480 -4 The lower left corner of the text block is
1482 positioned at ZFX, ZFY.
1483 -3 The center of the bottom edge is positioned at
1485 ZFX, ZFY.
1486 -2 The lower right corner is positioned at ZFX, ZFY.
1488 -1 The center of the left edge is positioned at ZFX,
1490 ZFY.
1491 0 (default) The text block is centered along both axes at
1493 ZFX, ZFY.
1494 1 The center of the right edge is positioned at
1496 ZFX, ZFY.
1497 2 The top left corner is positioned at ZFX, ZFY.
1499 3 The center of the top edge is positioned at ZFX,
1501 ZFY.
1502 4 The top right corner is positioned at ZFX, ZFY.
1504 ZFS - Zero Field Text Block Character Size - Real
1506 ZFS specifies the size of the characters used in the Zero Field
1507 graphics text block as a fraction of the viewport width. The
1508 default value is 0.033.
1509 ZFT - Zero Field Text String - Character* 36
1511 Use ZFT to modify the text of the Zero Field text block. The
1512 Zero Field text block may appear whenever the U and V vector
1513 component arrays contain data such that all the grid points
1514 otherwise eligible for plotting contain zero magnitude vectors.
1515 Currently the string length is limited to 36 characters. Set ZFT
1516 to a single space (´ ´) to prevent the text from being
1517 displayed. The default value for the text is ´Zero Field´.
1518 ZFX - Zero Field Text Block X Coordinate - Real
1520 ZFX establishes the X coordinate of the Zero Field graphics text
1521 block as a fraction of the viewport width. Values less than 0.0
1522 or greater than 1.0 are permissible and respectively represent
1523 regions to the left or right of the viewport. The actual
1524 position of the block relative to ZFX depends on the value
1525 assigned to the Zero Field Positioning Mode parameter, ZFP. The
1526 default value is 0.5.
1527 ZFY - Zero Field Text Block Y Coordinate - Real
1529 ZFY establishes the Y coordinate of the minimum vector graphics
1530 text block as a fraction of the viewport height. Values less
1531 than 0.0 or greater than 1.0 are permissible and respectively
1532 represent regions below and above the viewport. The actual
1533 position of the block relative to ZFY depends on the value
1534 assigned to the Zero Field Positioning Mode parameter, ZFP. The
1535 default value is 0.5.
1536
1538 Online: vectors, vvectr, vvgetc, vvgeti, vvgetr, vvinit, vvrset,
1539 vvsetc, vvseti, vvsetr. vvudmv, vvumxy, ncarg_cbind.
1540 Hardcopy: NCAR Graphics Fundamentals, UNIX Version
1542
1544 Copyright (C) 1987-2009
1545 University Corporation for Atmospheric Research
1546 The use of this Software is governed by a License Agreement.
1547UNIX April 1993 Vectors_params(3NCARG)