1PLCONT(3plplot)                   PLplot API                   PLCONT(3plplot)
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NAME

6       plcont - Contour plot
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SYNOPSIS

9       plcont(f, nx, ny, kx, lx, ky, ly, clevel, nlevel, pltr, pltr_data)
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DESCRIPTION

12       Draws a contour plot of the data in f[nx][ny], using the nlevel contour
13       levels specified by clevel. Only the region of the matrix from kx to lx
14       and  from  ky to ly is plotted out where all these index ranges are in‐
15       terpreted as one-based for historical reasons.  A  transformation  rou‐
16       tine pointed to by pltr with a generic pointer pltr_data for additional
17       data required by the transformation routine  is  used  to  map  indices
18       within the matrix to the world coordinates.
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20       Redacted form: plcont(f, kx, lx, ky, ly, clevel, pltr, pltr_data) where
21       (see above discussion) the pltr, pltr_data callback arguments are some‐
22       times replaced by a tr vector with 6 elements; xg and yg vectors; or xg
23       and yg matrices.
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25       This function is used in examples 9, 14, 16, and 22.
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ARGUMENTS

28       f (PLFLT_MATRIX(3plplot), input)
29              A matrix containing data to be contoured.
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31       nx, ny (PLINT(3plplot), input)
32              The dimensions of the matrix f.
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34       kx, lx (PLINT(3plplot), input)
35              Range of x indices to consider where 0 <=  kx-1  <  lx-1  <  nx.
36              Values  of  kx  and  lx are one-based rather than zero-based for
37              historical backwards-compatibility reasons.
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39       ky, ly (PLINT(3plplot), input)
40              Range of y indices to consider where 0 <=  ky-1  <  ly-1  <  ny.
41              Values  of  ky  and  ly are one-based rather than zero-based for
42              historical backwards-compatibility reasons.
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44       clevel (PLFLT_VECTOR(3plplot), input)
45              A vector specifying the levels at which to draw contours.
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47       nlevel (PLINT(3plplot), input)
48              Number of contour levels to draw.
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50       pltr (PLTRANSFORM_callback(3plplot), input)
51              A callback function that defines the transformation between  the
52              zero-based indices of the matrix f and the world coordinates.For
53              the C case, transformation functions are provided in the  PLplot
54              library:   pltr0(3plplot)   for   the   identity   mapping,  and
55              pltr1(3plplot) and pltr2(3plplot) for arbitrary mappings respec‐
56              tively defined by vectors and matrices.  In addition, C callback
57              routines for the transformation can be supplied by the user such
58              as  the  mypltr  function  in examples/c/x09c.c which provides a
59              general linear  transformation  between  index  coordinates  and
60              world  coordinates.For languages other than C you should consult
61              the PLplot documentation for the details concerning how PLTRANS‐
62              FORM_callback(3plplot)  arguments  are  interfaced.  However, in
63              general, a particular pattern of  callback-associated  arguments
64              such  as  a  tr vector with 6 elements; xg and yg vectors; or xg
65              and yg matrices are respectively interfaced to  a  linear-trans‐
66              formation   routine   similar  to  the  above  mypltr  function;
67              pltr1(3plplot); and pltr2(3plplot).  Furthermore,  some  of  our
68              more  sophisticated  bindings  (see, e.g., the PLplot documenta‐
69              tion) support native language callbacks for  handling  index  to
70              world-coordinate transformations.  Examples of these various ap‐
71              proaches are given  in  examples/<language>x09*,  examples/<lan‐
72              guage>x16*,   examples/<language>x20*,  examples/<language>x21*,
73              and examples/<language>x22*, for all our supported languages.
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75       pltr_data (PLPointer(3plplot), input)
76              Extra parameter to  help  pass  information  to  pltr0(3plplot),
77              pltr1(3plplot),  pltr2(3plplot),  or  whatever  callback routine
78              that is externally supplied.
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AUTHORS

82       Many developers (who  are  credited  at  http://plplot.org/credits.php)
83       have contributed to PLplot over its long history.
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SEE ALSO

86       PLplot documentation at http://plplot.org/documentation.php.
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90                                  July, 2023                   PLCONT(3plplot)
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