Re: [Matplotlib-users] marker plots

[Steve S. <el...@gm...>]

John Hunter wrote:
>>>>>>"Steve" == Steve Schmerler <el...@gm...> writes:
> 
> 
>     Steve> Hi I had some issues with marker plots and automatic color
>     Steve> cycling.
>     Steve> gives only black crosses. It would be nice if someone could
>     Steve> please try this out. My guess is that the "o"s and "v"s do
>     Steve> have some kind of black margin and a (colored) filling area
>     Steve> which the "+"s and "x"s dont't have. If that's right then
>     Steve> anyone should see this behavior. Thanx for your help.
> 
> As noted by Christian, the reason for this discrepancy is that '+' is
> not filled and 'o' is.  filled marker colors are governed by their
> 'markeredgecolor' and 'markerfacecolor'.  line styles are goverened by
> 'color'.  Thus it is not entirely trivial to determine how these three
> colors should behave in automatic color cycling.  For example, for
> filled markers, you might want the face color to automatically cycle
> and the edge colors to remain black (or more precisely, their default
> rc value).  For non-filled markers, which do not have a facecolor, you
> might want the edge color to cycle.
> 
> Could you specify how you think this should behave?  My guess is that
> this is sufficiently complicated that different people will want
> different default behaviors.  As you posted earlier, it is pretty
> simple to force the kind of cycling you want in your own code.  But if
> you can spell out a clear policy of how *it should* work, and there
> seems to be a consensus on this, or at least no objection, I can take
> a stab at implementing it in the axes code.  You can take a look
> yourself if you want Axes._process_plot_var_args and
> Axes._process_plot_format.
> 
> JDH
> 
> 
> 

Hi

Well, since mpl changes the markeredgecolor when you request 'r+' and 
the markerfacecolor when you say 'ro' it would be the most natural way 
to keep this behavior when "turning on" automatic cycling by

	rcParams["lines.marker"] = <any_marker>
	rcParams["lines.linestyle"] = "None"

Some would even suggest to let the markeredgecolor == markerfacecolor 
(if there is one) by default for the sake of some "consistency" (i.e. 
remove the markeredgecolor completely, like in gnuplot). I personally 
don't care.

Btw, the issue here applies only to pure marker plots (i.e. nothing like 
'o-') right? What if you want automatic cycling there?


The ideal behavior would be: Say you want to plot 30 data sets with 
lines _and_ markers like '+-'. There would be a call like


setAutoMarkerAndColor()
for i in range(...):
	A = load(<dataset>) # or whatever
	plot(A[:,0], A[:,1]) # no formating at all

which would then behave like


def getFormatString(i):
     # works for len(c) = len(m) and all i >= 0
     c = ['b', 'g', 'r']
     # maybe without '.' and ',' because they are pretty small
     m = ['o', 'x', 'v']
     max = len(c)*len(m) - 1
     if (i > max):
         ii = i - max - 1
     else:
         ii = i
     mind = int(floor(ii / len(m)))
     cind = ii - mind * len(m)
     return c[cind] + m[mind]

		
for i in range(...):
	A = load(<dataset>)
	fs = getFormatString(i)
	plot(A[:,0], A[:,1], fs)


Actually, that's very much it, except that it only works if the numbers 
of colors and markers are the same.


cheers,
steve

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