contourf filled level curves of a surface on a 2D plot

## Syntax

                contourf(x, y, z, nz, [style, strf, leg, rect, nax])

## Arguments

x, y

  two real row vectors of size `n1` and `n2`: the grid.

z

  a real matrix of size `(n1,n2)`, the values of the function.

nz

  the level values or the number of levels.

  -

    If `nz` is an integer, its value gives the number of level curves equally spaced from `zmin` to `zmax` as follows:

        z= zmin + (1:nz)*(zmax-zmin)/(nz+1)

    Note: that the `zmin` and `zmax` levels are not drawn (generically they are reduced to points) but they can be added with

        [im,jm] = find(z == zmin);     // or zmax
        plot2d(x(im)',y(jm)',-9,"000")

  -

    If `nz` is a vector, `nz(i)` gives the value of the `i`-th level curve.

style, strf, leg, rect, nax

  see `plot2d`. The argument `style` gives the colors which are to be used for level curves. It must have the same size as the number of levels.

## Description

`contourf` paints surface between two consecutive level curves of a surface `z=f(x,y)` on a 2D plot. The values of `f(x,y)` are given by the matrix `z` at the grid points defined by `x` and `y`.

You can change the format of the floating point number printed on the levels by using `xset("fpf",string)` where `string` gives the format in C format syntax (for example `string="%.3f"`). Use `string=""` to switch back to default format.

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

## Examples

    contourf(1:10,1:10,rand(10,10),5,1:5,"011"," ",[0,0,11,11])

contourf(1:10,1:10,rand(10,10),5,1:5,"011"," ",[0,0,11,11])

    function z=peaks(x,y)
    x1=x(:).*.ones(1,size(y,'*'));
    y1=y(:)'.*.ones(size(x,'*'),1);
    z =  (3*(1-x1).^2).*exp(-(x1.^2) - (y1+1).^2) ...
       - 10*(x1/5 - x1.^3 - y1.^5).*exp(-x1.^2-y1.^2) ...
       - 1/3*exp(-(x1+1).^2 - y1.^2)
    endfunction

    function z=peakit()
    x=-4:0.1:4;y=x;z=peaks(x,y);
    endfunction

    z=peakit();

    levels=[-6:-1,-logspace(-5,0,10),logspace(-5,0,10),1:8];
    m=size(levels,'*');
    n = fix(3/8*m);
    r = [(1:n)'/n; ones(m-n,1)];
    g = [zeros(n,1); (1:n)'/n; ones(m-2*n,1)];
    b = [zeros(2*n,1); (1:m-2*n)'/(m-2*n)];
    h = [r g b];
    gcf().color_map = h;
    xset('fpf',' ');
    clf();
    contourf([],[],z,[-6:-1,-logspace(-5,0,10),logspace(-5,0,10),1:8],0*ones(1,m))

    xset('fpf','');
    clf();
    contourf([],[],z,[-6:-1,-logspace(-5,0,10),logspace(-5,0,10),1:8]);

function z=peaks(x,y) x1=x(:).*.ones(1,size(y,'*')); y1=y(:)'.*.ones(size(x,'*'),1); z = (3*(1-x1).^2).*exp(-(x1.^2) - (y1+1).^2) ... - 10*(x1/5 - x1.^3 - y1.^5).*exp(-x1.^2-y1.^2) ... - 1/3*exp(-(x1+1).^2 - y1.^2) endfunction function z=peakit() x=-4:0.1:4;y=x;z=peaks(x,y); endfunction z=peakit(); levels=[-6:-1,-logspace(-5,0,10),logspace(-5,0,10),1:8]; m=size(levels,'*'); n = fix(3/8*m); r = [(1:n)'/n; ones(m-n,1)]; g = [zeros(n,1); (1:n)'/n; ones(m-2*n,1)]; b = [zeros(2*n,1); (1:m-2*n)'/(m-2*n)]; h = [r g b]; gcf().color_map = h; xset('fpf',' '); clf(); contourf([],[],z,[-6:-1,-logspace(-5,0,10),logspace(-5,0,10),1:8],0*ones(1,m))

## See also

- contour
- contour2d
- contour2di
- plot2d