contour_plot: can I get a logarithmic axis?



On 09/18/2011 04:04 PM, Andres Cimmarusti wrote:
>     contour_plot(
>        ytp(x,3,d,0), [d,-20,20], [x,0,1010], [grid,200,200], [legend,"Y"],
>        [gnuplot_preamble, "set key outside; set title 'Traveling plane
> wave, C = 3'; set cntrparam levels 10"] )$
>
> The center feature is barely noticeable, which is not what I want. I
> decided to try to use a logarithmic scale for my "y-axis" (really my
> x). So I tried using the option [logy] and got nothing as output.
> Decided then to try "set log y" in the gnuplot_preamble and again
> nothing.
>
> Is this feature available with contour_plot? or am I missing something?

Since x can be equal to zero, plotting the logarithmic scale can be 
problematic. Try

[x, 0.1, 10101]

for the domain.

If it doesn't work with contour_plot, you can try it with draw:

draw3d(xu_grid        = 200,
        yv_grid        = 200,
        contour_levels = 10,
        contour        = map,
        logy           = true,
        title          = "Traveling plane wave, C = 3",
        explicit(ytp(x,3,d,0), d,-20,20, x,0.1,1010) ) $

See the documentation for contour_levels and contour for extra control 
on isolines, or take a look at

http://riotorto.users.sourceforge.net/gnuplot/contours

--
Mario