`plshade1`: Shade individual region on the basis of value
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#### `plshade1`: Shade individual region on the basis of value

`plshade1 (` | 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`)`;

Shade individual region on the basis of value. Use `plshades` if you want to shade a number of contiguous regions using continuous colors. In particular the edge contours are treated properly in `plshades`. If you attempt to do contiguous regions with `plshade1` (or `plshade`) the contours at the edge of the shade are partially obliterated by subsequent plots of contiguous shaded regions. `plshade1` differs from `plshade` by the type of the first argument. Look at the argument list below, `plcont` and the section called “Contour and Shade Plots” for more information about the transformation from grid to world coordinates. Shading NEEDS DOCUMENTATION, but as a stopgap look at how `plshade` is used in `examples/c/x15c.c`

`a` (`const PLFLT *`, input)

  Contains array to be plotted. The array must have been declared as PLFLT a[nx][ny].

`nx` (`PLINT`, input)

  First dimension of array "a".

`ny` (`PLINT`, input)

  Second dimension of array "a".

`defined` (`PLINT (*) (PLFLT, PLFLT)`, input)

  User function specifying regions excluded from the shading plot. This function accepts x and y coordinates as input arguments and must return 0 if the point is in the excluded region or 1 otherwise. This argument can be NULL if all the values are valid.

`xmin` (`PLFLT`, input)

  Defines the "grid" coordinates. The data a[0][0] has a position of (xmin,ymin), a[nx-1][0] has a position at (xmax,ymin) and so on.

`xmax` (`PLFLT`, input)

  Defines the "grid" coordinates. The data a[0][0] has a position of (xmin,ymin), a[nx-1][0] has a position at (xmax,ymin) and so on.

`ymin` (`PLFLT`, input)

  Defines the "grid" coordinates. The data a[0][0] has a position of (xmin,ymin), a[nx-1][0] has a position at (xmax,ymin) and so on.

`ymax` (`PLFLT`, input)

  Defines the "grid" coordinates. The data a[0][0] has a position of (xmin,ymin), a[nx-1][0] has a position at (xmax,ymin) and so on.

`shade_min` (`PLFLT`, input)

  Defines the lower end of the interval to be shaded. If shade_max ≤ shade_min, `plshade1` does nothing.

`shade_max` (`PLFLT`, input)

  Defines the upper end of the interval to be shaded. If shade_max ≤ shade_min, `plshade1` does nothing.

`sh_cmap` (`PLINT`, input)

  Defines color map. If ``sh_cmap`=0`, then ``sh_color`` is interpreted as a color map 0 (integer) index. If ``sh_cmap`=1`, then ``sh_color`` is interpreted as a color map 1 floating-point index which ranges from 0. to 1.

`sh_color` (`PLFLT`, input)

  Defines color map index if cmap0 or color map input value (ranging from 0. to 1.) if cmap1.

`sh_width` (`PLFLT`, input)

  Defines width used by the fill pattern.

`min_color` (`PLINT`, 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`, 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`, 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`, 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` (`void (*) (PLINT, const PLFLT *, const PLFLT *)`, input)

  Routine used to fill the region. Use `plfill`. Future version of plplot may have other fill routines.

`rectangular` (`PLBOOL`, 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` (`void (*) (PLFLT, PLFLT, PLFLT *, PLFLT *, PLPointer)` , input)

  Pointer to function that defines transformation between indices in array ``z`` and the world coordinates (C only). Transformation functions are provided in the PLplot library: `pltr0` for identity mapping, and `pltr1` and `pltr2` for arbitrary mappings respectively defined by one- and two-dimensional arrays. In addition, user-supplied routines for the transformation can be used as well. Examples of all of these approaches are given in the section called “Contour Plots from C”. The transformation function should have the form given by any of `pltr0`, `pltr1`, or `pltr2`.

`pltr_data` (`PLPointer`, input)

  Extra parameter to help pass information to `pltr0`, `pltr1`, `pltr2`, or whatever routine that is externally supplied.

Redacted form:

- General: `plshade1(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)`

- Perl/PDL: `plshade1(a, xmin, xmax, ymin, ymax, shade_min, shade_max, sh_cmap, sh_color, sh_width, min_color, min_width, max_color, max_width, fill, rectangular, defined, pltr, pltr_data)`

This function is used in example 15.

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