--- name: "plshade" section: "3plplot" platform: "linux" package: "plplot-doc" version: "5.15.0+dfsg2-15" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/plshade" --- # plshade(3plplot) Shade individual region on the basis of value ## NAME **plshade** - Shade individual region on the basis of value ## SYNOPSIS **plshade**(*a*, *nx*, *ny*, *defined*, *xmin*, *xmax*, *ymin*, *ymax*, *shade\_min*, *shade\_max*, *sh\_cmap*, *sh\_color*, *sh\_width*, *min\_color*, *min\_width*, *max\_color*, *max\_width*, *fill*, *rectangular*, *pltr*, *pltr\_data*) ## DESCRIPTION Shade individual region on the basis of value. Use [**plshades**(3plplot)](/plshades/3plplot.md) if you want to shade a number of contiguous regions using continuous colors. In particular the edge contours are treated properly in [**plshades**(3plplot)](/plshades/3plplot.md). If you attempt to do contiguous regions with [**plshade**(3plplot)](/plshade/3plplot.md) the contours at the edge of the shade are partially obliterated by subsequent plots of contiguous shaded regions. Redacted form: General: **plshade(a, defined, xmin, xmax, ymin, ymax, shade\_min, shade\_max, sh\_cmap, sh\_color, sh\_width, min\_color, min\_width, max\_color, max\_width, fill, rectangular, pltr, pltr\_data)** This function is used in example 15. ## ARGUMENTS - *a* (**PLFLT\_MATRIX**(3plplot), input) A matrix containing function values to plot. Should have dimensions of *nx* by *ny*. - *nx* (**PLINT**(3plplot), input) First dimension of the matrix "a". - *ny* (**PLINT**(3plplot), input) Second dimension of the matrix "a". - *defined* (**PLDEFINED\_callback**(3plplot), input) Callback function specifying the region that should be plotted in the shade plot. This function accepts x and y coordinates as input arguments and must return 1 if the point is to be included in the shade plot and 0 otherwise. If you want to plot the entire shade plot (the usual case), this argument should be set to NULL. - *xmin, xmax, ymin, ymax* (**PLFLT**(3plplot), input) See the discussion of *pltr* below for how these arguments are used (only for the special case when the callback function *pltr* is not supplied). - *shade\_min* (**PLFLT**(3plplot), input) Defines the lower end of the interval to be shaded. If shade\_max \<= shade\_min, [**plshade**(3plplot)](/plshade/3plplot.md) does nothing. - *shade\_max* (**PLFLT**(3plplot), input) Defines the upper end of the interval to be shaded. If shade\_max \<= shade\_min, [**plshade**(3plplot)](/plshade/3plplot.md) does nothing. - *sh\_cmap* (**PLINT**(3plplot), input) Defines color map. If *sh\_cmap*=0, then *sh\_color* is interpreted as a cmap0 (integer) index. If *sh\_cmap*=1, then *sh\_color* is interpreted as a cmap1 argument in the range (0.0-1.0). - *sh\_color* (**PLFLT**(3plplot), input) Defines color map index with integer value if cmap0 or value in range (0.0-1.0) if cmap1. - *sh\_width* (**PLFLT**(3plplot), input) Defines width used by the fill pattern. - *min\_color* (**PLINT**(3plplot), input) Defines pen color, width used by the boundary of shaded region. The min values are used for the shade\_min boundary, and the max values are used on the shade\_max boundary. Set color and width to zero for no plotted boundaries. - *min\_width* (**PLFLT**(3plplot), input) Defines pen color, width used by the boundary of shaded region. The min values are used for the shade\_min boundary, and the max values are used on the shade\_max boundary. Set color and width to zero for no plotted boundaries. - *max\_color* (**PLINT**(3plplot), input) Defines pen color, width used by the boundary of shaded region. The min values are used for the shade\_min boundary, and the max values are used on the shade\_max boundary. Set color and width to zero for no plotted boundaries. - *max\_width* (**PLFLT**(3plplot), input) Defines pen color, width used by the boundary of shaded region. The min values are used for the shade\_min boundary, and the max values are used on the shade\_max boundary. Set color and width to zero for no plotted boundaries. - *fill* (**PLFILL\_callback**(3plplot), input) Routine used to fill the region. Use [**plfill**(3plplot)](/plfill/3plplot.md). Future version of PLplot may have other fill routines. - *rectangular* (**PLBOOL**(3plplot), input) Set *rectangular* to true if rectangles map to rectangles after coordinate transformation with *pltrl*. Otherwise, set *rectangular* to false. If *rectangular* is set to true, plshade tries to save time by filling large rectangles. This optimization fails if the coordinate transformation distorts the shape of rectangles. For example a plot in polar coordinates has to have *rectangular* set to false. - *pltr* (**PLTRANSFORM\_callback**(3plplot), input) A callback function that defines the transformation between the zero-based indices of the matrix *a* and world coordinates. If *pltr* is not supplied (e.g., is set to NULL in the C case), then the x indices of *a* are mapped to the range *xmin* through *xmax* and the y indices of *a* are mapped to the range *ymin* through *ymax*.For the C case, transformation functions are provided in the PLplot library: **pltr0**(3plplot) for the identity mapping, and **pltr1**(3plplot) and **pltr2**(3plplot) for arbitrary mappings respectively defined by vectors and matrices. In addition, C callback routines for the transformation can be supplied by the user such as the mypltr function in examples/c/x09c.c which provides a general linear transformation between index coordinates and world coordinates.For languages other than C you should consult the PLplot documentation for the details concerning how **PLTRANSFORM\_callback**(3plplot) arguments are interfaced. However, in general, a particular pattern of callback-associated arguments such as a tr vector with 6 elements; xg and yg vectors; or xg and yg matrices are respectively interfaced to a linear-transformation routine similar to the above mypltr function; **pltr1**(3plplot); and **pltr2**(3plplot). Furthermore, some of our more sophisticated bindings (see, e.g., the PLplot documentation) support native language callbacks for handling index to world-coordinate transformations. Examples of these various approaches are given in examples/\x09\*, examples/\x16\*, examples/\x20\*, examples/\x21\*, and examples/\x22\*, for all our supported languages. - *pltr\_data* (**PLPointer**(3plplot), input) Extra parameter to help pass information to **pltr0**(3plplot), **pltr1**(3plplot), **pltr2**(3plplot), or whatever routine that is externally supplied. ## AUTHORS Many developers (who are credited at http://plplot.org/credits.php) have contributed to PLplot over its long history. ## SEE ALSO PLplot documentation at http://plplot.org/documentation.php.