matplotlib-devel Mailing List for matplotlib

Hi
I'm having some problems with the formatter of ticks in a polar plot.
Below is a minimum example
The first figure is correct, the second has wrong ticks.
This has be tested both on 1.2.0 and the latest from git (1.4.x, commit
64cc3416396ffb2811af80fc810ed63572df71d9 )
Does anyone know whys this happens?
Is it a bug in MaxNLocator
Kind regards
Pål
---------------------------
#!/usr/bin/env python
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.ticker import MaxNLocator
# Data
M=np.sin(np.meshgrid(np.arange(30),np.arange(30)))
M=np.squeeze(M[0,:,:])
Radius=np.arange(30)
Theta=np.arange(30)
# Plotting the correct figure
print('Correct ticks')
fig=plt.figure()
ax1 = fig.add_axes([0,0,0.8,1],projection='polar')
c = ax1.pcolormesh(Theta, Radius, M)
ax1.set_frame_on(False)
plt.xticks([])
plt.yticks([])
ax2=fig.add_axes([0.9,0.1,0.05,0.7])
cb=fig.colorbar(c,cax=ax2)
plt.show()
# Doing the same plot
print('Wrong ticks by using formatter')
fig=plt.figure()
ax1 = fig.add_axes([0,0,0.8,1],projection='polar')
c = ax1.pcolormesh(Theta, Radius, M)
ax1.set_frame_on(False)
plt.xticks([])
plt.yticks([])
ax2=fig.add_axes([0.9,0.1,0.05,0.7])
cb=fig.colorbar(c,cax=ax2)
# except now setting a limit to the number of ticks using a formatter
# which results in wrong ticks
cb.ax.yaxis.set_major_locator(MaxNLocator(3))
plt.show()
-----------------------

Hi,
It was great to meet many of the Matplotlib developers at SciPy 2013. I had
a great time and I learnt a huge amount, which I am slowly starting to
digest.
In particular, without the Matplotlib sprint, I would never have got off
the ground -- many thanks to all those who took the time to be patient with
me!
I have been working, as a first step, on colored line support. This is not,
of course, new -- it's all in LineCollection. However, as a user,
LineCollection is intimidating and difficult to understand, and does not
lead to easy experimentation (I speak from experience).
At Tony's suggestion, the first step was to rewrite the
multicolored_line.py example.
You can find my first attempt as an IPython notebook at
https://github.com/dpsanders/matplotlib-examples/blob/master/linecolor.ipynb
or
http://nbviewer.ipython.org/urls/raw.github.com/dpsanders/matplotlib-examples/master/linecolor.ipynb
Please let me have any comments before I attempt the next step of making a
pull request.
It seems to me that IPython notebooks are quite a natural format for such
examples, especially with a view to having interactive examples in the
future.
I have tried, as discussed in the sprint, to separate the data processing
from the plotting.
The function "linecolor" (the only other reasonable name that I thought of
was "colorline") should be able to be extracted without too much effort
(hopefully?) into the axes module and into pyplot.
What is the situation with tagging the examples? If the examples are being
refactored, it would seem to at least be a natural moment to start adding
tags, even if nothing is actually done with them yet.
Along these lines, it seems to me that there is a lot of other
functionality which is difficult to get at for the average user who does
not understand collections or patches.
For example, there is an 'arrow' function in pyplot, which just exposes the
FancyArrow patch, but there is no corresponding 'circle', 'ellipse' etc.
function for those patches.
I think this would be a great addition -- what is the general consensus?
By the way, I only understood what an 'axes' object is yesterday, even
though I have been using Matplotlib for several years. The documentation
that I found seems to assume that the user is coming from Matlab and
already implicitly understands what 'axes' refers to.
Some more general comments which I have been led to in this process:
- Ben made the comment that it was very important to have figures in the
documentation for each function. I completely agree with this. It seems to
me that a simple way to achieve this would be to have one example for each
function, with the name of the example file being the same as the name of
the function (à la Matlab!) Thus I have (re-)named the script as
"linecolor.py".
- At the moment, there seem to be too many places with examples:
screenshots, examples, gallery, scipy cookbook, figures for each function,
etc.
I think that the (refactored) gallery is the solution, and is where people
should be pointed -- the screenshots page and the examples page do not seem
to me to be useful / necessary.
- Also during the BoF / sprint, style sheets were discussed several times.
Tony seems to have already solved this problem in his mpltools package -- I
would suggest that this could be brought straight into Matplotlib?
Thanks to everybody for a great package (and for reading all this, if you
get this far). Please let me know if this is (not) the right place to
discuss such things.
Best wishes,
David.
-- 
**************************************************************************
Dr. David P. Sanders
Profesor Titular A / Associate Professor
Departamento de Física, Facultad de Ciencias
Universidad Nacional Autónoma de México (UNAM)
dps...@gm...
http://sistemas.fciencias.unam.mx/~dsanders
Cubículo / office: #414
Tel.: +52 55 5622 4965