A matrix containing data to be contoured.

The dimensions of the matrix f.

Range of x indices to consider where 0 ≤ kx-1 < lx-1 < nx. Values of kx and lx are one-based rather than zero-based for historical backwards-compatibility reasons.

Range of y indices to consider where 0 ≤ ky-1 < ly-1 < ny. Values of ky and ly are one-based rather than zero-based for historical backwards-compatibility reasons.

A vector specifying the levels at which to draw contours.

Number of contour levels to draw.

A callback function that defines the transformation between the zero-based indices of the matrix f and the world coordinates.

For the C case, transformation functions are provided in the PLplot library: pltr0 for the identity mapping, and pltr1 and pltr2 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 Part III, “ Supported computer languages ” for the details concerning how PLTRANSFORM_callback 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; and pltr2. Furthermore, some of our more sophisticated bindings (see, e.g., Chapter 10, Fortran Language) support native language callbacks for handling index to world-coordinate transformations. Examples of these various approaches are given in examples/<language>x09*, examples/<language>x16*, examples/<language>x20*, examples/<language>x21*, and examples/<language>x22*, for all our supported languages.

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