contour2di

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.

xc,yc

vectors of identical sizes containing the contours definitions. See below for details.

Description

contour2di computes 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.

xc(1) contains the level associated with first contour path, yc(1) contains the number N1 of points defining this contour path and (xc(1+(1:N1)), yc(1+(1:N1)) ) contain the coordinates of the paths points. The second path begin at xc(2+N1) and yc(2+N1) and so on.

Examples

[xc,yc]=contour2di(1:10,1:10,rand(10,10),5);
k=1;n=yc(k);c=1;
while k+yc(k)<size(xc,'*')
  n=yc(k);
  plot2d(xc(k+(1:n)),yc(k+(1:n)),c)
  c=c+1;
  k=k+n+1;
end

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
• contour2d — 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 This function is obsolete.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.