contour2di

compute level curves of a surface on a 2D plot

Calling Sequence

[xc,yc]=contour2di(x,y,z,nz)

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 (obsolete function)
• fcontour2d Level curves of a surface defined by a function on a 2D plot (obsolete function)
• contour2d level curves of a surface on a 2D plot
• plot2d 2D plot
• xset set values of the graphics context.This function is obsolete.