[Matplotlib-users] A bug in stem?

[<na...@te...>]

Greetings,

Matplotlib has been helping me a lot, as always. I post so
infrequently to this group because I usually don't have any
problem getting what I want. However, I think I found a bug
in stem.

I've been stressing the stem function a lot, since I deal
with signal processing. When plotting a demonstration of the
overlap and save method (for performing long convolutions),
I got something unexpected which the script below reproduces:

---
from matplotlib.pylab import *

n = arange(0, 2*pi, 2*pi/50, Float)
x = sin(n)

figure(1)
stem(n, x, "k-", "ko", "k-")

x[:26] = 0

savefig("test.eps")
---

The sequence is plotted almost without any problems: the
vertical lines are drawn with the correct amplitudes, but,
because of the setting of some values of x to 0, the markers
"fall down" to the axes. If I couldn't make myself clear, I
can send an image of the result, but I think the script can
reproduce the problem. I'm using the latest version of
matplotlib, downloaded and installed yesterday.

As it turns out, it actually *helped* me. Overlapp and save
method consists in discarding some samples of the result. I
couldn't think of a good way to actually show in a single
figure how it would be done. I mention the bug, if it is really
a bug, and not me doing something wrong, only to report it. I
have no hurry to see it fixed - in fact, as it helped me, I
don't plan to have it fixed soon. But I thought the developers
would like to know it.

Also, I would like to know if there is any way to customize
the markers. There are some figures I need to make where the
markers should be arrows pointing up. I modified "^" to look
like what I wanted, but probably there is a better way to do
that.

Thanks in advance

---
José Alexandre Nalon
na...@te...