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

6       VVINIT - Performs initialization tasks required before VVECTR may be
7       called to plot a vector field, including copying array size information
8       into internal common block variables, establishing coordinate system
9       mappings and boundaries, determining the maximum and minimum vector
10       magnitudes and scalar array values, and, if required, setting up the
11       color threshold value array.
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SYNOPSIS

14       CALL VVINIT (U,LU,V,LV,P,LP,M,N,WRK,LW)
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C-BINDING SYNOPSIS

17       #include <ncarg/ncargC.h>
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19       void c_vvinit(float *u, int lu, float *v, int lv,
20                     float *p, int lp, int m, int n,
21                     float *wrk, int lw)
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DESCRIPTION

24       U           (REAL 2-dimensional array, dimensioned LU x n: n >= N,
25                   input): By default, assumed to contain the first
26                   dimensional Cartesian components of the vector field.
27                   However, if PLR is non-zero, it is treated as containing
28                   the vector magnitudes.
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30       LU          (INTEGER, input): Actual value of the first dimension of
31                   array U.
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33       V           (REAL 2-dimensional array, dimensioned LV x n: n >= N,
34                   input): By default, assumed to contain the second
35                   dimensional Cartesian components of the vector field.
36                   However, if PLR is non-zero, it is treated as containing
37                   the vector angles.
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39       LV          (INTEGER, input): Actual value of the first dimension of
40                   array V
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42       P           (REAL 2-dimensional array, dimensioned LP x n: n >= N,
43                   input): Array of scalar data that may be used to color the
44                   vectors. The grid points are assumed to coincide with the
45                   grid points of the U and V arrays. Required only if CTV has
46                   an absolute value of 2; otherwise this argument is ignored
47                   and may be assigned a dummy value.
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49       LP          (INTEGER, input): Actual value of the first dimension of
50                   array P
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52       M           (INTEGER, input): Number of contiguous elements along the
53                   first dimensional axis containing data to be processed in
54                   each of the arrays, U, V, and P (if used).
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56       N           (INTEGER, input): Number of contiguous elements along the
57                   second dimensional axis containing data to be processed in
58                   each of the arrays, U, V, and P (if used).
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60       WRK         (REAL, array dimensioned n: n >= LW, input/output): Work
61                   array required only if the parameter VMD is set to a value
62                   greater than 0.0. If required must be dimensioned greater
63                   or equal to 2 * M * N. Otherwise may be set to a dummy
64                   value.
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66       LW          (INTEGER, input): Assumed size of the array WRK. If the
67                   parameter VMD is set to a value greater than 0.0, must be
68                   set to a value less than or equal to the dimension of the
69                   WRK array, but greater or equal to 2 * M * N. Otherwise,
70                   this argument should be assigned the integer value 0.
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C-BINDING DESCRIPTION

73       The C-binding argument descriptions are the same as the FORTRAN
74       argument descriptions with the following exceptions:
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77       lu          The second dimension of u in the calling program.
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79       lv          The second dimension of v in the calling program.
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81       lp          The second dimension of p in the calling program.
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83       m           Number of contiguous elements along the second dimensional
84                   axis containing data to be processed in each of the arrays,
85                   u, v, and p (if used).
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87       n           Number of contiguous elements along the first dimensional
88                   axis containing data to be processed in each of the arrays,
89                   u, v, and p (if used).
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USAGE

92       Call VVINIT before the first invocation of VVECTR and again anytime you
93       modify the contents of the input data arrays. You may precede a VVINIT
94       call with any number of calls to the Vectors parameter setting routines
95       (VVSETC, VVSETI, or VVSETR). After the VVINIT call, you may still
96       change certain parameters before calling VVECTR. (Consult the
97       vectors_params man page for further information on this point.)
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99       Set up the two vector component arrays prior to calling VVINIT.  To
100       permit multiple purpose use of the array space, the VVINIT argument
101       list includes both the actual size and an assumed size for the first
102       dimension of each input array. Due to FORTRAN array ordering
103       conventions, only the assumed size needs to be specified for the second
104       dimension.  (Note: when using the C bindings, mentally exchange all
105       references to first and second dimensions in this discussion.) The
106       arguments LU, LV, and LP contain the actual size of the first
107       dimensions of arrays U, V, and P respectively. Since the grid locations
108       for each of the data arrays are assumed to coincide, a single argument,
109       M, represents the assumed size of the first dimension for all the
110       arrays.  Similarly, the argument, N, is the assumed size of the second
111       dimension. The only requirement for the actual second dimension size is
112       that it be greater than or equal to N for each array.
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114       The array specified by the WRK argument and its associated size
115       specifier, LW, are used only when the parameter VMD (Vector Minimum
116       Distance) is given a value greater than 0.0. In this case, Vectors uses
117       the array to keep track of the location of each vector in NDC space so
118       that the distances between vectors can be compared. Based on these
119       comparisons, Vectors eliminates some vectors such that the remaining
120       vectors are separated by at least the specified distance. If VMD is
121       less than or equal to 0.0, you may assign an arbitrary dummy value to
122       WRK, but you should set LW to the integer value 0.
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C-BINDING USAGE

125       C-Binding usage is the same as FORTRAN usage discussed above if the
126       references to "first dimension" and "second dimension" are exchanged.
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EXAMPLES

129       Use the ncargex command to see the following relevant examples: bnchmk,
130       fcover, ffex00, ffex01, ffex02, ffex05, stex02, stex03, vvex01, vvex02.
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ACCESS

133       To use VVINIT or c_vvinit, load the NCAR Graphics libraries ncarg,
134       ncarg_gks, and ncarg_c, preferably in that order.
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MESSAGES

137       See the vectors man page for a description of all Vectors error
138       messages and/or informational messages.
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SEE ALSO

141       Online: vectors, vectors_params, vvectr, vvgetc, vvgeti, vvgetr,
142       vvrset, vvsetc, vvseti, vvsetr, vvudmv, vvumxy, ncarg_cbind.
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144       Hardcopy: NCAR Graphics Fundamentals, UNIX Version
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147       Copyright (C) 1987-2009
148       University Corporation for Atmospheric Research
149       The use of this Software is governed by a License Agreement.
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153UNIX                              April 1993                    VVINIT(3NCARG)
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