contourf

filled level curves of a surface on a 2D plot

Calling Sequence

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 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 ith 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 consecutives 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.

Sample

Examples

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];
`xset`_('colormap',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]);

See Also

• contour level curves on a 3D surface
• fcontour level curves on a 3D surface defined by a function (obsolete function)
• fcontour2d Level curves of a surface defined by a function on a 2D plot (obsolete function)
• contour2di compute level curves of a surface on a 2D plot
• plot2d 2D plot
• xset set values of the graphics context.This function is obsolete.