1Vectors(3NCARG)                  NCAR GRAPHICS                 Vectors(3NCARG)
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NAME

6       Vectors - Utility for creating a vector field plot given two arrays
7       containing the vector components on a uniform grid. In addition, the
8       user may pass in another array of scalar data defined over the same
9       grid space independent of but presumably related in some fashion to the
10       vector data. The utility will then color each vector based on the
11       scalar value at the grid point. Alternatively, the user can choose to
12       color the vectors based on vector magnitude.
13

SYNOPSIS

15       The following two calls are the minimum required to create a vector
16       field plot using the current interface:
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18       ·      VVINIT - Performs the initialization required for VVECTR to
19              interpret the input array data properly. VVINIT stores the data
20              array sizes, sets up various coordinate system mappings, and
21              processes the input arrays to find the maximum and minimum
22              values. If vector coloring is enabled and the user has not
23              explicitly taken control, the routine establishes a linearly
24              scaled color threshold array.
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26       ·      VVECTR - Renders the vectors based on conditions established by
27              VVINIT and the current values of a set of user-modifiable
28              internal parameters associated with the Vectors utility.
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30       All user-modifiable internal parameters have default values; only those
31       which are to have values different from the default need to be set. The
32       routines used to set Vectors parameters are as follows:
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34       ·      VVRSET - Resets all internal parameters to their default values.
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36       ·      VVSETC - Assigns a value of type CHARACTER to a parameter.
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38       ·      VVSETI - Assigns a value of type INTEGER to a parameter.
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40       ·      VVSETR - Assigns a value of type REAL to a parameter.
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42       In general, once a parameter is given a value by a call to one of these
43       routines, it retains that value until a similar call resets it.
44       Retrieve the value of an internal parameter by calling one of the
45       following routines:
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47       ·      VVGETC - Returns a parameter value of type CHARACTER.
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49       ·      VVGETI - Returns a parameter value of type INTEGER.
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51       ·      VVGETR - Returns a parameter value of type REAL.
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53       ·
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55       Vectors supports three obsolete routines for compatibility with old
56       NCAR Graphics codes. The compatibility mode parameter, CPM, offers a
57       number of options that allow considerable flexibility in making the
58       transition to the new version of the utility. When writing new code you
59       are encouraged not to use these entry points, since they provide less
60       capability than the standard Vectors interface, and may eventually be
61       phased out.
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63       ·      VELVCT - The principal entry point prior to Version 3.2, now a
64              front end to the VVINIT/VVECTR interface.
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66       ·      EZVEC - Front end to VELVCT: a simpler interface for standard
67              situations, when detailed control of the plot is not required.
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69       ·      VELVEC - Older version of VELVCT and now also a front end to it.
70              It differs from the VELVCT call only in that it contains one
71              less input argument in its calling sequence.
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C-BINDING SYNOPSIS

74       c_vvinit
75       c_vvectr
76       c_vvrset
77       c_vvsetc
78       c_vvseti
79       c_vvsetr
80       c_vvgetc
81       c_vvgeti
82       c_vvgetr
83       c_velvct
84       c_ezvec
85       c_velvec
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USER-MODIFIABLE INTERNAL ROUTINES

88       The following routines are not to be called directly. However, you may
89       modify them in order to customize the behavior of Vectors. VVUMXY is
90       provided to support user-defined mapping transformations. VVUDMV allows
91       you to tailor vector masking to your requirements.
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93       ·      VVUMXY - Performs a user-definable mapping of vector position
94              and direction from data coordinate space to normalized device
95              coordinate space.
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97       ·      VVUDMV - The default name of a routine used to draw vectors
98              masked to an area map. VVUDMV decides which segments of a vector
99              to draw depending on the area group and group identifier arrays
100              passed to it.
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ACCESS

103       To use Vectors, load the NCAR Graphics libraries ncarg, ncarg_gks, and
104       ncarg_c, preferably in that order.
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MESSAGES

107       In this section are listed, in alphabetical order, all the error
108       messages that may be written by Vectors. Each error message begins with
109       the name of the Vectors routine in which an error has been detected,
110       followed by a dash, followed by the error message itself. These error
111       messages are written by a call to the error-handling support routine
112       SETER, with a final argument indicating that the error is fatal and
113       that execution should be terminated.
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115       VVECTR - TOO MANY AREA GROUPS
116              The area map passed as the argument, IAM, to VVECTR contains
117              more area groups than allowed by the Vectors utility, currently
118              64. This error can occur only if the Mask to Area Map parameter,
119              MSK, has a value greater than 0, specifying that vectors are to
120              be drawn masked to an area map.
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122       VVECTR - INVALID AREA MAP
123              The area map passed as the argument, IAM, to VVECTR is judged to
124              be invalid because it contains a negative value for the number
125              of area groups. This error can occur only if the Mask to Area
126              Map parameter, MSK, has a value greater than 0, specifying that
127              vectors are to be drawn masked to an area map.
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129       VVGETC - PARAMETER NAME NOT KNOWN - x
130              The given parameter name (´x´) is not a legal parameter name
131              known to Vectors.
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133       VVGETC - PARAMETER NAME TOO SHORT - x
134              The parameter name ("x") is less than three characters long.
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136       VVGETI OR VVGETR - GETTING x - PAI INCORRECT
137              An attempt has been made to get an element of the parameter
138              array named ´x´ and the current value of PAI (the "parameter
139              array index") is inappropriate for that parameter array.
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141       VVGETI OR VVGETR - PARAMETER NAME NOT KNOWN - x
142              The given parameter name (´x´) is not a legal parameter name
143              known to Vectors.
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145       VVGETI OR VVGETR - PARAMETER NAME TOO SHORT - x
146              The parameter name ("x") is less than three characters long.
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148       VVINIT - U AND/OR V ARRAY DIMENSIONS EXCEEDED
149              The VVINIT input argument, M, specifying the number of array
150              elements to use along the first dimension of the U and V (and
151              possibly P) arrays, exceeds the actual first dimension of U
152              and/or V, as specified by the input arguments LU and LV.
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154       VVINIT - SCALAR ARRAY TOO SMALL
155              The value given to LP, the VVINIT input argument specifying the
156              actual first dimension of the scalar data array, P, is less than
157              M, the input argument specifying the number of array elements to
158              use along the first dimension for all of the input arrays. This
159              error can only occur when the absolute value of the Color
160              Threshold Level control parameter, CTV, is set to 2, indicating
161              that coloring is to be performed according to values contained
162              in the scalar data array, P.
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164       VVSETC - PARAMETER NAME NOT KNOWN - x
165              The given parameter name (´x´) is not a legal parameter name
166              known to Vectors.
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168       VVSETC - PARAMETER NAME TOO SHORT - x
169              The parameter name ("x") is less than three characters long.
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171       VVSETI OR VVSETR - PARAMETER NAME NOT KNOWN - x
172              The given parameter name (´x´) is not a legal parameter name
173              known to Vectors.
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175       VVSETI OR VVSETR - PARAMETER NAME TOO SHORT - x
176              The parameter name ("x") is less than three characters long.
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178       VVSETI OR VVSETR - PARAMETER VALUE OUT OF RANGE - x
179              An attempt has been made to set the parameter named ´x´ to a
180              value outside the range allowed by the Vectors utility.
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182       VVSETI OR VVSETR - SETTING x - PAI INCORRECT
183              An attempt has been made to set an element of the parameter
184              array named ´x´ and the current value of PAI (the "parameter
185              array index") is inappropriate for that parameter array.
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SEE ALSO

188       Online: vectors_params, ezvec, velvec, velvct, fx, fy, vvectr, vvgetc,
189       vvgeti, vvgetr, vvinit, vvrset, vvsetc, vvseti, vvsetr, vvudmv, vvumxy,
190       ncarg_cbind.
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192       Hardcopy: NCAR Graphics Fundamentals, UNIX Version
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195       Copyright (C) 1987-2009
196       University Corporation for Atmospheric Research
197       The use of this Software is governed by a License Agreement.
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201UNIX                              April 1993                   Vectors(3NCARG)
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