Re: [Matplotlib-users] Multiprocessing and matplotlib

[Sameer Grover]

It's a backend issue:the code works with wxagg but not with gtkagg.

On 1 November 2010 00:54, Sameer Grover  wrote:
> Can matplotlib be used in scripts with multiple processes, such as
> when using the multiprocessing module?
>
> I had some difficulty getting code to work in which I was carrying out
> some long computations and wanted to show intermediate results in a
> separate process so as not to interrupt the main computation. The
> problem distilled down to trying to use the multiprocessing module and
> matplotlib together. This is a code snippet which I expected to work,
> but doesn't. Is this a matplotlib issue, some intricate issue with
> GUIs and processes, or something with my understanding of the subject?
>
> Would you expect this code to work? Is there any easy workaround?
>
> from pylab import *
> import multiprocessing
> class myclass(object):
>    def plotter(self):
>        plot([1,2,3,4])
>        show()
>    def mainfunction(self):
>        a = arange(1, 10, 0.1)
>        newprocess = multiprocessing.Process(target=self.plotter)
>        newprocess.start()
>        newprocess.join()
>        plot(a, sin(a))
>        show()
> if __name__== '__main__':
>    a = myclass()
>    a.mainfunction()
>
> Thanks,
> Sameer
>

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Re: [Matplotlib-users] Error on matplotlib with the hist() method [ archlinux ]

[daryl herzmann]

On Sun, 31 Oct 2010, David Kremer wrote:

>  File "/usr/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py",

python 2.7 ^^

> RuntimeError: Could not open facefile /usr/lib/python2.6/site-
> packages/matplotlib/mpl-data/fonts/ttf/Vera.ttf; Cannot_Open_Resource

python 2.6 ^^

I believe this problem is fixed in the next matplotlib release.  A 
workaround is to remove a local font cache file:

rm ~/.matplotlib/fontList.cache

HTH,
daryl

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$10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing
Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store 
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[Matplotlib-users] Auto-wrapping text within a plot... Is there a simpler solution?

[Joe Kington]

Hi folks,

First off, I apologize for the wall of text...

Spurred on by this Stack Overflow
question,
and by an itch I've been wanting to scratch lately, I put together a a
callback function that (attempts, anyway) to auto-wrap text artists to the
boundaries of the axis they're in.

It is often useful to have text reflow/auto-wrap within the axis boundaries
during interactive use (resizing a plot with lots of labeled points, for
example...).  It doesn't really need to be precise, as long as it keeps
words from being fully off the figure.

A "full" gui toolkit would be a better way of handling this, but I've gotten
in the habit of slapping a few callback functions onto matplotlib figures to
make (simple) interactive scripts that I can share across platforms. (Lab
exercises, in my case.) Having a way to make text reflow within the axis
boundaries during resizing of plots makes things a bit easier.

I'm aware that this isn't really possible in a general, backend-independent
fashion due to the subtleties of text rendering in matplotlib (e.g. things
like latex, where the length of the raw string has nothing to do with it's
rendered size, and the general fact that the size of the text isn't known
until after it's drawn).Even getting it approximately correct is still
useful, though.

I have it working about as well as the approach I'm taking can do, I think,
but I could use some help on a couple of points.

I have two specific questions, and one more general one...

First:
Is it possible to disconnect and then reconnect a callback function from an
event within the callback function, and without disconnecting all other
callback functions from the event?

I'm redrawing the canvas within a "draw_event" callback function, and I'm
currently avoiding recursion by disconnecting and reconnecting all callbacks
to the draw event. It would be nice to disconnect only the function I'm
inside, but I can't find any way of getting its cid...

Alternatively, is there a way to redraw a figure's canvas without triggering
a draw event?

Second:
Is there any way to determine the average aspect ratio of a font in
matplotlib?

I'm trying to approximate the length of a rendered text string based on it's
font size and the number of characters. Currently, I'm assuming that all
fonts have an average aspect ratio of 0.5, which works decently for most
non-monospaced fonts, but fails miserably with others.

Finally:
Is there a better way to do this? My current approach has tons of
limitations but works in most situations.  My biggest problem so far is that
vertical alignment in matplotlib (quite reasonably) refers to an
axis-aligned bounding box, rather than within a text aligned bounding box.
This makes reflowing rotated text more difficult, and I'm only half-way
dealing with rotated text in the code below.  Any suggestions on any points
are welcome!

Thanks!
-Joe

import matplotlib.pyplot as plt

def main():
fig = plt.figure()
plt.plot(range(10))

t = "This is a really long string that I'd rather have wrapped so that
it"\
" doesn't go outside of the figure, but if it's long enough it will go"\
" off the top or bottom!"
plt.text(7, 3, t, ha='center', rotation=30, va='center')
plt.text(5, 7, t, fontsize=18, ha='center')
plt.text(3, 0, t, family='serif', style='italic', ha='right')
plt.title("This is a really long title that I want to have wrapped so
it"\
 " does not go outside the figure boundaries")
fig.canvas.mpl_connect('draw_event', on_draw)
plt.show()

def on_draw(event):
import matplotlib as mpl
fig = event.canvas.figure

# Cycle through all artists in all the axes in the figure
for ax in fig.axes:
for artist in ax.get_children():
# If it's a text artist, wrap it...
if isinstance(artist, mpl.text.Text):
autowrap_text(artist, event.renderer)

# Temporarily disconnect any callbacks to the draw event...
# (To avoid recursion)
func_handles = fig.canvas.callbacks.callbacks[event.name]
fig.canvas.callbacks.callbacks[event.name] = {}
# Re-draw the figure..
fig.canvas.draw()
# Reset the draw event callbacks
fig.canvas.callbacks.callbacks[event.name] = func_handles

def autowrap_text(textobj, renderer):
import textwrap
from math import sin, cos
# Get the starting position of the text in pixels...
x0, y0 = textobj.get_transform().transform(textobj.get_position())
# Get the extents of the current axis in pixels...
clip = textobj.get_axes().get_window_extent()

# Get the amount of space in the direction of rotation to the left and
# right of x0, y0
# (This doesn't try to correct for different vertical alignments, and
will
# have issues with rotated text when va & ha are not 'center')
dx1, dx2 = x0 - clip.x0, clip.x1 - x0
dy1, dy2 = y0 - clip.y0, clip.y1 - y0
rot

[Matplotlib-users] Can't force draw

[starz1010101]

I can't force pyplot to draw in the middle a function.  For example, this
function does not plot the sine before the user prompt, only after the
entire function executes:

import matplotlib.pyplot as plt
import numpy as np

def plot_now():
  plt.ion()
  plt.figure()
  x = 2*np.pi*np.linspace(0.0, 1.0, 100)
  plt.plot( x, np.sin(x) )
  plt.draw()
  plt.draw()
  q  = raw_input( 'anything: ')

I'm using the enthought python distribution for mac in ipython.  




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$10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing
Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store 
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[Matplotlib-users] Ticks direction

[Bartosz Telenczuk]

Hi all,

Is it possible to set direction (in or out) individually for each tick. I know 
about the rc setting ("(x/y)tick.direction") , but I need a finer control over 
the ticks.

Thanks,

Bartek

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Create new apps & games for the Nokia N8 for consumers in  U.S. and Canada
$10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing
Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store 
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[Matplotlib-users] colormaps - combine linear segmented with discrete sections?

[Timothy W. Hilton]

Hello,

I have a 2D numpy masked array of geo-located data -- with some data
missing -- that I wish to plot on a map.  Basemap provides a nice tool
to do this, but I am stumped trying to get the colorscheme I want.

My data are only physically meaningful on land, so I am using
Basemap.maskoceans() to mask out "wet" locations (oceans, lakes, etc.)
Trouble is, now both water as well as actual missing data show up in
the missing data color.

I want to have blue water, some other (bright) color for missing data,
and a nice-looking color transition (matplotlib.cm.Blues or something
similar) for the valid data over land (values from 0 to 50).  The
Cookbook example at

addresses my problem, but I cannot get it to work.  After changing
instances of matplotlib.numerix to numpy, I get a long list of
exceptions, the last of which is 
TypeError: __call__() got an unexpected keyword argument 'bytes'.  
This has to do with sentinelNorm, I think, but I'm not sure how to fix it.

Eventually I would like to sub-classify missing data by the type of
missing input that caused a missing value, but for now a single
missing data color is enough.

The code below does almost what I want- I just need to figure out how
to make the water blue.  I have also messed around with
matplotlib.cm.BoundaryNorm to create a colormap/normalization to
handle my data, but I am getting hung up initializing the cmap,
counting bin edges, etc.  I also tacked my test code for that...  Any
help greatly appreciated!

Thanks,
Tim

--

Timothy W. Hilton
PhD Candidate, Department of Meteorology
The Pennsylvania State University
503 Walker Building, University Park, PA   16802
hil...@meteo.psu.edu

#--
# amost right...

import numpy as np
import numpy.ma as ma
from mpl_toolkits.basemap import Basemap, maskoceans
import matplotlib.pyplot as plt
import matplotlib.colors

if __name__=="__main__":

# setup a basemap instance & draw a map
m_aeqd = Basemap(width=9e5,height=9e5,projection='aeqd',
 lat_0=28.46,lon_0=360-80.67, resolution='i', 
area_thresh=1000,
 rsphere=6371007.181000)
col_water='#B9D3EE'  #SlateGray2
col_land ='#1C1C1C'
m_aeqd.drawmapboundary(fill_color=col_water)
# draw coasts and fill continents.
m_aeqd.drawcoastlines(linewidth=0.5)
m_aeqd.fillcontinents(color=col_land,lake_color=col_water, zorder=0)


# create a 100 x 100 pseudodata array with valid data between 0
  and 50 and some "missing" data (less than zero)
n=100
X = ma.masked_less(np.random.random_integers(-1, 50, (n,n)), 0)
plot_mid = np.mean((m_aeqd.llcrnrx, m_aeqd.urcrnrx))
Xu, Xv = np.meshgrid(np.arange(stop=plot_mid + 500*n,
   start=plot_mid - 500*n, step=1000),
 np.arange(stop=m_aeqd.urcrnry,
   start=m_aeqd.urcrnry - 1000*n, step=1000))
Xlon, Xlat = m_aeqd(Xu, Xv, inverse=True)

#setup a colormap and plot the data
cmap = matplotlib.cm.get_cmap("Blues", 25)
#mask oceans
ocean_mask = maskoceans(Xlon, Xlat, X)
#now I'm stumped how to incorporate oceans_mask into the color map
oceans_cmap = matplotlib.colors.ListedColormap((col_land, "#00"),
   name="oceans", N=2)
cmap.set_bad(color="#FF")  #show missing vals in bright red
m_aeqd.pcolormesh(Xu, Xv, ocean_mask, cmap=cmap)
plt.colorbar()


#it seems like I could do another pcolormesh call with
#ocean_mask.mask and oceans_cmap; I'd need to set the
#transparency.  It seems like the more elegant solution is to
#devise cmap to account for ocean_mask.mask (water) separately
#from X.mask (data that are actually missing).  I'm not sure how
#do that though.

--
Nokia and AT&T present the 2010 Calling All Innovators-North America contest
Create new apps & games for the Nokia N8 for consumers in  U.S. and Canada
$10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing
Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store 
http://p.sf.net/sfu/nokia-dev2dev
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