On Mon, Apr 23, 2012 at 5:09 AM, jul tayon <jta...@gmail.com> wrote:
> Hello list
>
> matplotlib website says this mailing is the prefered way to report
> bug, so here I am :
>
> System :
> python ; 2.7.2+
> matplotlib 1.1.0
> ubuntu TLS amd64
> matplotlib Backend : TkAgg
>
>
> How to reproduce (on my pf)
> Code Snippet :
>
> ######CODE
>
> import matplotlib
> import matplotlib.pyplot as p
> import random
> y = random.randint(0,10000000)
> p.plot( [ int( y * ( 1 - 0.0006)) , y])
> p.show()
>
> ######ENDCODE
>
> Exected Result :
> https://github.com/jul/pypi-stat/blob/master/why.png
>
> Cause ?
>
> It stinks something like a rounding error on the float.
> If it also happens in Qt/Gtk backend it might be a matplotlib bug, if
> it is only in Tk then it is either a Tk or a TkAgg bug.
>
> Cheers,
> --
> Jul
>
Sorry, I'm not clear on what the bug is. Is the picture you link to the
*expected* result or the result from *executing* the code snippet. There
are some inconsistencies between the pic and the code (legend, time on
xaxis, 3 point in pic, title), so it's a bit unclear what you're referring
to.
If you're talking about the offset value added to the y-axis, it's actually
not a bug; it's a feature (usually that's a joke, but in this case, I'm
serious).
This feature is useful when you have large numbers that vary over small
ranges. Maybe it's not so bad in your example, but for larger numbers with
smaller ranges (see code snippet below), it's quite helpful. I thought
there was an rc parameter to tweak the value for using offsets, but I can't
seem to find it. Below I create a custom tick formatter and turn offsets.
There may be a better way to do this.
If this isn't the bug you were suggesting, please clarify.
Best,
-Tony
#~~~~~
import matplotlib.pyplot as plt
fig, ax = plt.subplots()
# or `ax = plt.gca()` for older versions of matplotlib
y = 1e9
ax.plot([y, y+1])
ax.yaxis.set_major_formatter(plt.ScalarFormatter(useOffset=False))
plt.show()
#~~~~~
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