Revision history [back]

One can use gnuplot (in Sage)

   sage: gnuplot_console()
    #and then
    set contour surface
    set cntrparam levels incremental -14,4,13
    unset surface 
    set isosamples 100,100
    splot [-4:4] [-4:4] [-13:13] x**2-y**2

One can use gnuplot (in Sage)

   sage: gnuplot_console()
    #and then
    set contour surface
    set cntrparam levels incremental -14,4,13
-10,2,10
    unset surface 
    set isosamples 100,100
    splot [-4:4] [-4:4] [-13:13] [-11:11] x**2-y**2