# pcolor

## Purpose

Pseudocolor plot.

## Synopsis

    pcolor(C)
    pcolor(x,y,C)
    pcolor(X,Y,C)
    h = pcolor(...)

## Description

`pcolor(C)` draws a pseudocolor plot, a rectangular array of cells with colors determined by the elements of `C`. A pseudocolor plot is actually a surface plot seen from the top. MATLAB creates this type of plot by using each set of four adjacent points in `C` to define a patch object.

With the default shading mode, `faceted`, each cell has a constant color determined by the corner with the smallest xy coordinates, and the last row and column of `C` are not used. With `interp` shading, each cell has color resulting from bilinear interpolation of the color at its four vertices and all elements of `C` are used. The mapping from `C` to `color` is defined by `colormap` and `caxis`.

`pcolor(x,y,C)` with two vector arguments must have `length(x) = n` and `length(y) = m` where `[m,n] = size(C)`. The spacing of the grid lines is set by `x` and `y`, so the grid lines are straight, but not necessarily evenly spaced. Note that `x` corresponds to the columns of `C` and `y` corresponds to the rows.

`pcolor(X,Y,C)` has three matrix arguments, all the same size. A logically rectangular, two-dimensional grid is drawn with vertices at the points `[X(i,j), Y(i,j)]`. The color in the `(i,j)`th cell is determined by `C(i,j)` if shading is `faceted` or `flat`, or by interpolation between the colors at the four vertices if shading is `interp`.

`pcolor` is closely related to `surf`; in fact, `pcolor(X,Y,C)` is the same as viewing `surf(X,Y,0`*`Z,C)` from above, that is, `view([0 90])`.

`pcolor` and `image` are similar, but`pcolor(C)` specifies the colors of vertices whereas `image(C)` specifies the colors of cells and directly indexes into the colormap with no scaling. Consequently, the number of vertices for `pcolor(C)` is the same as the number of cells for `image(C)`. With three arguments, `pcolor(X,Y,C)` can produce parametric grids, which are not possible with `image`.

`h = pcolor(...)` returns a handle to a `surface` object. `surface` objects are children of `axes`.

## Examples

A Hadamard matrix has elements which are +1 and -1, so a colormap with only two entries is appropriate.

    pcolor(hadamard(20))
    colormap(gray(2))
    axis('ij')
    axis('square')

``A simple color wheel illustrates a polar coordinate system.

    n = 6;
    r = (0:n)'/n;
    theta = pi*(-n:n)/n;
    X = r*cos(theta);
    Y = r*sin(theta);
    C = r*cos(2*theta);
    pcolor(X,Y,C)
    axis('square')

## See Also

    image, surf, view

(c) Copyright 1994 by The MathWorks, Inc.