contour2d

contour2d — level curves of a surface on a 2D plot

Calling sequence

contour2d(x,y,z,nz,[style,strf,leg,rect,nax])  
contour2d(x,y,z,nz,<opt_args>)

Parameters

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.

<opt_args> : This represents a sequence of statements key1=value1, key2=value2,... where key1, key2,... can be one of the following: style, leg, rect, nax, strf or axesflag and frameflag (see plot2d)

style,strf,leg,rect,nax : see plot2d. The argument style gives the dash styles or colors which are to be used for level curves. It must have the same size as the number of levels.

Description

contour2d draws 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 and Use string=" " to suppress printing.

The optional arguments style,strf,leg,rect,nax, can be passed by a sequence of statements key1=value1, key2=value2, ... where keys may be style,strf,leg,rect,nax. In this case, the order has no special meaning.

Use contour to draw levels curves on a 3D surface.

Enter the command contour2d() to see a demo.

Examples



contour2d(1:10,1:10,rand(10,10),5,rect=[0,0,11,11])
// changing the format of the printing of the levels
xset("fpf","%.2f")
xbasc()
contour2d(1:10,1:10,rand(10,10),5,rect=[0,0,11,11])

Author

J.Ph.C.