contourf

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.

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
• fcontour2d — level curves of a surface defined by a function on a 2D plot
• 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 This function is obsolete.

Authors

J.Ph.C.