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Contour_plot

Function: contour_plot (<expr>, <x_range>, <y_range>, <options>, ...) It plots the contours (curves of equal value) of <expr> over the region <x_range> by <y_range>. Any additional arguments are treated the same as in plot3d.

This function only works when the plot format is either gnuplot or gnuplot_pipes. The additional package implicit_plot can also be used to plot contours and it works for any format. See implicit_plot.

Examples:

          (%i1) contour_plot (x^2 + y^2, [x, -4, 4], [y, -4, 4])$

          (%i1) F(x, y) := x^3 + y^2;
                                             3    2
          (%o1)                  F(x, y) := x  + y
          (%i2) contour_plot (F, [u, -4, 4], [v, -4, 4])$

You can add any options accepted by plot3d; for instance, the option legend with a value of false, to remove the legend. Gnuplot chooses, by default, 3 contours to show. to increase the number of levels, it is necessary to specify a custom gnuplot preamble:

          (%i1) contour_plot (u^3 + v^2, [u, -4, 4], [v, -4, 4],
          (%i2) [legend,false], [gnuplot_preamble,"set cntrparam levels 12"])$

(%o1)                                true
(%i2)