[Matplotlib-users] Controlling zorder of individual elements of the same type...

[Fernando P. <Fer...@co...>]

Hi all,

I am having a bit of a problem with the order things get drawn.  I looked at 
the zorder example and the docs, but I can't seem to find a solution.  Here's 
an illustration:

http://amath.colorado.edu/faculty/fperez/tmp/zorder_prob.png

The red wiggly line is drawn first, by a loglog() call, and then the green one 
is an axhline() call.  However, the green line ends up below the red one.  It 
turns out that in cases where the range of the red stuff is above the green 
cutoff, this causes the green line to be totally obscured.  And for my plots, 
it's important that the green line is clearly visible always.

My naive expectation was that whatever was called last on the plot would end 
up on top, but that doesn't seem to be the case.  I did a few experiments:

x=frange(0,2*pi,npts=100)
figure()
plot(x,sin(x),x,cos(x),linewidth=10)
plot(x,sin(2*x),linewidth=10)
axhline(0,linewidth=10)

And I can't really figure out what determines the zorder of all the line objects.

Is there a way to control this?  Would it make sense to make the default 
behavior something more like what hand-drawing would cause?  I mean: you draw 
on the canvas as if it were paper, and newly drawn lines appear on top of 
older ones.

Maybe there's a good reason for the current design, and I'm just missing the 
proper incantation.  I'd be very grateful for a pointer in the right direction.

Cheers,

f