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Operators and Keywords

Function List:

C++ API

: contour (z)
: contour (z, vn)
: contour (x, y, z)
: contour (x, y, z, vn)
: contour (…, style)
: contour (hax, …)
: [c, h] = contour (…)

Create a 2-D contour plot.

Plot level curves (contour lines) of the matrix z, using the contour matrix c computed by contourc from the same arguments; see the latter for their interpretation.

The appearance of contour lines can be defined with a line style style in the same manner as plot. Only line style and color are used; Any markers defined by style are ignored.

If the first argument hax is an axes handle, then plot into this axis, rather than the current axes returned by gca.

The optional output c contains the contour levels in contourc format.

The optional return value h is a graphics handle to the hggroup comprising the contour lines.

Example: 

x = 0:2;
y = x;
z = x' * y;
contour (x, y, z, 2:3)

See also: ezcontour, contourc, contourf, contour3, clabel, meshc, surfc, caxis, colormap, plot.

Demonstration 1

The following code

 clf;
 colormap ("default");
 [x, y, z] = peaks ();
 contour (x, y, z);
 title ({"contour() plot (isolines of constant Z)"; "Z = peaks()"});

Produces the following figure

Figure 1

Demonstration 2

The following code

 clf;
 colormap ("default");
 [theta, r] = meshgrid (linspace (0,2*pi,64), linspace (0,1,64));
 [X, Y] = pol2cart (theta, r);
 Z = sin (2*theta) .* (1-r);
 contour (X, Y, abs (Z), 10);
 title ({"contour() plot"; "polar fcn: Z = sin (2*theta) * (1-r)"});

Produces the following figure

Figure 1

Demonstration 3

The following code

 clf;
 colormap ("default");
 z = peaks ();
 contour (z, [0 0]);
 title ({"contour() plot with single isoline at Z == 0"; "Z = peaks()"});

Produces the following figure

Figure 1

Package: octave