Plotting, hold-on, colors

[David Bateman]

Ben Boxman wrote:
>   Setting colors manually works if you are dealing with a "simple" plot
> (though this is somewhat annoying). This becomes a bit more "icky" if you're
> using other functions that end up calling plot (for instance: hist, pwelch,
> or a user function) -- there is a work-around (in that you can receive the
> raw plot data, and then call plot (or bar), rewrite said user function to
> set a color externally (in lieu of the default color)), but this requires
> multiple steps + setting colors for each and every one.
>   (e.g. two hists() with hold on also aren't satisfactory)
>
>   My primary reason for using octave is convenience --  I can both process &
> visualize my data (which is often produced by a non-octave environment) --
> and I can do both in a simple/efficient manner -- which I can't do, as
> easily, outside of octave.
>
> Ben
>   

The behavior you describe is the Matlab compatible behavior, and many 
users seem to want strict compatibility. That being said I can think of 
an easy way to get the behavior you want. Try overloading the 
__next_line_color__ function. For example add the function

function rgb = __next_line_color__ (reset)

  persistent color_rotation = [];
  persistent num_colors = [];
  persistent color_index = [];

  if (nargin < 2)
    if (nargin == 1 && reset)
      color_rotation = get (gca (), "colororder");
      num_colors = rows (color_rotation);
      ## Don't reset the color_index except if this is first call
      if (isempty (color_index) || color_index > num_colors)
        color_index = 1;
      endif
    else
      ## Need this as original __next_line_color__ called first
      if (! isempty (color_rotation))
    color_rotation = get (gca (), "colororder");
    num_colors = rows (color_rotation);
      endif
      if (isempty (color_index))
        color_index = 1;
      endif

      rgb = color_rotation(color_index,:);
      if (++color_index > num_colors)
        color_index = 1;
      endif
      color_index
      rgb
    endif
  else
    print_usage ();
  endif

endfunction

in the front of your path. The color_index variable is never reset in 
the above and so you'll cycle through the plot colors even if 
__next_line_color__(true) is called to reset it.

D.



-- 
David Bateman                                David.Bateman at motorola.com
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