grayplot 2D plot of a surface using colors

## Syntax

    grayplot(x,y,z,[strf,rect,nax])
                grayplot(x,y,z,<opt_args>)

## Arguments

x,y

  real row vectors of size n1 and n2.

z

  real matrix of size (n1,n2). `z(i,j)` is the value of the surface at the point (x(i),y(j)).

<opt_args>

  This represents a sequence of statements `key1=value1, key2=value2` ,... where `key1`, `key2,...` can be one of the following: rect, nax, strf, logflag or axesflag and frameflag (see `plot2d`).

strf,rect,nax

  see `plot2d`.

## Description

`grayplot` makes a 2D plot of the surface given by `z` on a grid defined by `x` and `y`. Each rectangle on the grid is filled with a gray or color level depending on the average value of `z` on the corners of the rectangle. If z contains %nan values, the surrounding rectangles are not displayed.

Enter the command `grayplot()` to see a demo.

## Examples

    x=-10:10;
    y=-10:10;
    m=rand(21,21);
    grayplot(x,y,m,rect=[-20,-20,20,20])

x=-10:10; y=-10:10; m=rand(21,21); grayplot(x,y,m,rect=[-20,-20,20,20])

    t=-%pi:0.1:%pi;
    m=sin(t)'*cos(t);
    clf()
    grayplot(t,t,m)

t=-%pi:0.1:%pi; m=sin(t)'*cos(t); clf() grayplot(t,t,m)

## See also

- fgrayplot
- plot2d
- Sgrayplot
- Sfgrayplot

## History

5.5.0 Option `logflag` introduced.