matplotlib-users Mailing List for matplotlib (Page 3)

Hi Marek,

I just installed Matplotlib via gentoo's emerge (a first for me) and had no=
=20
problem with from pylab import *. I think you may need to take it up with=20
your sysadmin. Make sure dev-python/matplotlib is added to your=20
package.keywords file. The 0.80 version is stable, although it is masked as=
=20
testing (~) in the gentoo tree.

Darren


On Wednesday 25 May 2005 7:40 pm, Marek Szczypinski wrote:
> Hello,
> I am new to matplotlib. My system administrator installed matplotlib
> (using gentoo's emerge command). There were no errors while installation,
> but wen i try to import pylab i get an error:
>
> markacy@sun:~>python
> Python 2.3.5 (#1, Apr 28 2005, 10:18:07)
> [GCC 3.3.5-20050130 (Gentoo Linux 3.3.5.20050130-r1, ssp-3.3.5.20050130-1,
> pie- on linux2
> Type "help", "copyright", "credits" or "license" for more information.
>
> >>> from pylab import *
>
> Traceback (most recent call last):
>    File "<stdin>", line 1, in ?
> ImportError: No module named pylab
>
>
> What is the problem??
> Thanks,
> Marek
>
>
> Homo sum, humani nihil a me alienum puto.
>
>
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=2D-=20
Darren S. Dale

Bard Hall
Department of Materials Science and Engineering
Cornell University
Ithaca, NY. 14850

dd...@co...
http://people.ccmr.cornell.edu/~dd55/

Marek Szczypinski wrote:
> Hello,
> I am new to matplotlib. My system administrator installed matplotlib 
> (using gentoo's emerge command). There were no errors while 
> installation, but wen i try to import pylab i get an error:
> 
> markacy@sun:~>python
> Python 2.3.5 (#1, Apr 28 2005, 10:18:07)
> [GCC 3.3.5-20050130 (Gentoo Linux 3.3.5.20050130-r1, 
> ssp-3.3.5.20050130-1, pie- on linux2
> Type "help", "copyright", "credits" or "license" for more information.
> 
>>>> from pylab import *
> 
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> ImportError: No module named pylab

 >>> from matplotlib.pylab import *

or, better:

$ ipython -pylab

-- 
Robert Kern
rk...@uc...

"In the fields of hell where the grass grows high
  Are the graves of dreams allowed to die."
   -- Richard Harter

Hello,
I am new to matplotlib. My system administrator installed matplotlib 
(using gentoo's emerge command). There were no errors while installation, 
but wen i try to import pylab i get an error:

markacy@sun:~>python
Python 2.3.5 (#1, Apr 28 2005, 10:18:07)
[GCC 3.3.5-20050130 (Gentoo Linux 3.3.5.20050130-r1, ssp-3.3.5.20050130-1, 
pie- on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from pylab import *
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
ImportError: No module named pylab
>>>

What is the problem??
Thanks,
Marek


Homo sum, humani nihil a me alienum puto.

I'm trying to define a custom colormap that is blue for -ve values, red 
for +ve values, and white at 0.  To this end, I've defined a new 
colormap with the following entries:

_redblue_data = {'red':  ((0.0, 0.0, 0.0),(0.5, 1.0, 1.0),(1.0, 1.0, 1.0)),
                'green': ((0.0, 0.0, 0.0),(0.5, 1.0, 1.0),(1.0, 0.0, 0.0)),
                'blue':  ((0.0, 1.0, 1.0),(0.5, 1.0, 1.0),(1.0, 0.0, 0.0))}

However, when I use this to plot a contourf of my data (setting the 
contour levels to be 0), the contour just below 0 is light blue, and the 
contour just above 0 is white.  In other words, instead of being 
symmetrical, the 'center' of the colormap is shifted towards the +ve.  
Is there any way to make the colormap symmetric around 0?

I'm using matplotlib-0.80.

Jordan

>>>>> "Jeff" == Jeff Peery <jef...@se...> writes:

    Jeff> Thanks John, Well I don't know why I'm not using WXAgg, I'm
    Jeff> fairly new to this matplotlib stuff. I'm using wxpython,
    Jeff> will wxAgg work with this? Thanks.

Yes, the wx backend is something of a historical artifact.  Around
matplotlib-0.50, Perry Greenfield suggested using the antigrain
library as a core image renderer, and transfer this image into the
respective graphical user interfaces.  This idea came from Eric Jones
and Chaco.  This simplifies development enormously because we don't
have to deal with the idiosyncrasies of all the GUI drawing
libraries.  

The WXAgg backend in general will look a lot better and have more
features than the plain vanilla wx backend.  It is slower than we
would like it to be, because we are not using the most efficient
method to transfer the agg canvas to wx, and it doesn't have all the
save formats as wx does.  For example, I noticed your attached image
was jpg.  wxagg doesn't support jpeg, but uses png instead.  This is a
good thing.  You will be much happier with your wxagg png images than
you are with wx jpeg images I suspect.

JDH

Thanks John,

Well I don't know why I'm not using WXAgg, I'm fairly new to this
matplotlib stuff. I'm using wxpython, will wxAgg work with this? Thanks.

Jeff

-----Original Message-----
From: John Hunter [mailto:jdh...@ni...] 
Sent: Wednesday, May 25, 2005 11:43 AM
To: Jeff Peery
Cc: mat...@li...
Subject: Re: [Matplotlib-users] y label positioning

>>>>> "Jeff" == Jeff Peery <jef...@se...> writes:

    Jeff> Hi, yes I attached an image and a piece of my script
    Jeff> (frame2.py). What do you think? Thanks.

I see.  This looks like a WX bug -- could you file a sourceforge bug
report and include your two files you attached?  


Is there a reason you are not using WXAgg?  This will probably fix
this problem for you and make nicer figures too..

import matplotlib
matplotlib.use('WXAgg')
from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as
FigureCanvas
from matplotlib.backends.backend_wx import NavigationToolbar2Wx

JDH 

>>>>> "Jeff" == Jeff Peery <jef...@se...> writes:

    Jeff> Hi, yes I attached an image and a piece of my script
    Jeff> (frame2.py). What do you think? Thanks.

I see.  This looks like a WX bug -- could you file a sourceforge bug
report and include your two files you attached?  


Is there a reason you are not using WXAgg?  This will probably fix
this problem for you and make nicer figures too..

import matplotlib
matplotlib.use('WXAgg')
from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as FigureCanvas
from matplotlib.backends.backend_wx import NavigationToolbar2Wx

JDH 

Hi, yes I attached an image and a piece of my script (frame2.py). What
do you think? Thanks.



-----Original Message-----
From: John Hunter [mailto:jdh...@ni...] 
Sent: Wednesday, May 25, 2005 9:56 AM
To: Jeff Peery
Cc: mat...@li...
Subject: Re: [Matplotlib-users] y label positioning

>>>>> "Jeff" == Jeff Peery <jef...@se...> writes:

    Jeff> Hello, I don't know if my last email was posted so I'll try
    Jeff> again. Is there a way to position a y axis label?  By
    Jeff> default it seems to be placed directly over the y-axis tick
    Jeff> marks and looks really bad. Thanks.

Could you post a script that replicates your problem, and possibly an
image.  Also the result of running your script with --verbose-helpful.

Thanks,
JDH

>>>>> "Jeff" == Jeff Peery <jef...@se...> writes:

    Jeff> Hello, I don't know if my last email was posted so I'll try
    Jeff> again. Is there a way to position a y axis label?  By
    Jeff> default it seems to be placed directly over the y-axis tick
    Jeff> marks and looks really bad. Thanks.

Could you post a script that replicates your problem, and possibly an
image.  Also the result of running your script with --verbose-helpful.

Thanks,
JDH

Hello, I don't know if my last email was posted so I'll try again. Is
there a way to position a y axis label?  By default it seems to be
placed directly over the y-axis tick marks and looks really bad. Thanks.

Jeff

mencoder is part of mplayer.

http://www.mplayerhq.hu/homepage/design7/news.html

N.

Nils Wagner wrote:

> Hi all,
>
> I can't find mencoder on my system (SuSE Linux 9.1).
> Any pointer would be appreciated.
>
> Thanks in advance
>                                      Nils

On May 25, 2005, at 10:00 AM, Nils Wagner wrote:
>
> I can't find mencoder on my system (SuSE Linux 9.1).
> Any pointer would be appreciated.

The `mencoder' program comes with mplayer, the swiss army chainsaw of 
linux media players.  There are SuSE 9.1 RPMs at
	
	http://wiki.version6.net/RPM

I don't have access to a SuSE system right now, so I haven't been able 
to test 'em myself, but it's worth a try.

Ken

Hi all,

I can't find mencoder on my system (SuSE Linux 9.1).
Any pointer would be appreciated.

Thanks in advance
                                      Nils





          

>>>>> "Nicholas" == Nicholas Young <su...@su...> writes:

    Nicholas> With this the apparent problem moved from from
    Nicholas> matplotlib to my code where I guess the real problem is
    Nicholas> - I guess when python does garbage disposal - and using
    Nicholas> a different matplotlib version somehow triggered it.

Do you have any homegrown extension code in your project?  Always an
important detail ... <wink>

JDH

On Tue, 2005-05-24 at 12:53 -0500, John Hunter wrote: 
> Compile mpl with VERBOSE =  True in setup.py which will help inform
> where the segfault is occurring.  You will want to rm -rf your build
> dir to force a clean debug build.

With this the apparent problem moved from from matplotlib to my code
where I guess the real problem is - I guess when python does garbage
disposal - and using a different matplotlib version somehow triggered
it.

Thanks for the help,
Nich

>>>>> "Jeff" == Jeff Peery <jef...@se...> writes:

    Jeff> Hello, can anyone give me a few pointers for getting py2exe

Have you seen this?

http://matplotlib.sourceforge.net/faq.html#PY2EXE

JDH

Hello, can anyone give me a few pointers for getting py2exe to work with
matplotlib? I'm having some trouble. I get a warning that the 'runtime
has ended unexpectedly.' I had a similar problem before I started using
matplotlib in my wxpython applications because for some reason python
didn't like numarray.  I removed all occurrences of it and replaced it
with Numeric which solved my problem.  Also it didn't like it when I
imported modules using 'from'. So I replaced them with 'import'.
Although since I started using matplotlib I added "from" in my header
which now looks like this:

import wxFrame1
import wxDialog4
import wx
import matplotlib
matplotlib.use('WX')

from matplotlib.backends.backend_wx import FigureCanvasWx as
FigureCanvas
from matplotlib.backends.backend_wx import NavigationToolbar2Wx
from matplotlib.backends.backend_wx import _load_bitmap
from matplotlib.figure import Figure
from matplotlib.mlab import normpdf

I am not sure how to change the "from's" to "import's" here and I also
don't know why when I run py2exe it searches for numarray ( I know this
because py2exe tells me its missing ) Anyhow I'm not sure any of this is
related to the current problem. If anyone has some experience with
getting py2exe working with matplotlib I would appreciate the help.
Thanks.

>>>>> "Ken" == Ken McIvor <mc...@ii...> writes:

    Ken> In retrospect, "more consistent" was a poor choice of words.
    Ken> I believe I was thinking of some corner case where I had to
    Ken> do something like `obj.member.set_text("blah")' when I wrote
    Ken> it.  Of course, I cannot find an example where you have to do
    Ken> this, so it's a good bet I was doing something daft.

No, this is pretty common.  Eg,

 ax.xaxis.major.formatter

and so on.  But I think this kind of organization is OK.  Especially
in ipython, with tab completion :-)

JDH

On May 24, 2005, at 1:42 PM, John Hunter wrote:
>>>>>> "Ken" == Ken McIvor <mc...@ii...> writes:
>
>     Ken> I'm all for having more consistent accessors for the various
>     Ken> object properties.  Perhaps something like this would work
>     Ken> well?  (yeah, it's modeled on Tkinter's configure() method)
>
> Well, the current approach is nothing if not consistent.  The whole
> "set" functionality is based upon the objects having property
> setters.  Eg, set(PROPERTYNAME=val) always calls
> set_PROPERTYNAME(val)

In retrospect, "more consistent" was a poor choice of words.  I believe 
I was thinking of some corner case where I had to do something like 
`obj.member.set_text("blah")' when I wrote it.  Of course, I cannot 
find an example where you have to do this, so it's a good bet I was 
doing something daft.

>     Ken> If anyone else is interested in working to develop a tutorial
>     Ken> for matplotlib's OO API, please drop me a line... I have a
>     Ken> vested interest in making matplotlib easier for busy
>     Ken> developers to use.
>
> I suggest extending Robert's tutorial linked here
>
>   http://matplotlib.sourceforge.net/faq.html#OO

This tutorial looks like a great place to start.  Thanks!

Ken 

>>>>> "Ken" == Ken McIvor <mc...@ii...> writes:

    Ken> I'm all for having more consistent accessors for the various
    Ken> object properties.  Perhaps something like this would work
    Ken> well?  (yeah, it's modeled on Tkinter's configure() method)

    Ken> 	# def set(cfgdict=None, **kwds) -> None
    Ken> x.set(facecolor='r', size=2)

Well, the current approach is nothing if not consistent.  The whole
"set" functionality is based upon the objects having property
setters.  Eg, set(PROPERTYNAME=val) always calls
set_PROPERTYNAME(val)

The set function you propose is a good idea and trivial to write.
Just add this function to matplotlib.artist.Artist

    def set(self, **kwargs):
        """
        A tkstyle set command, pass kwargs to set properties
        """
        ret = []
        for k,v in kwargs.items():
            k = k.lower()
            funcName = "set_%s"%k
            func = getattr(self,funcName)
            ret.extend( [func(v)] )
        return ret

I'll include this in the next release.



    Ken> If anyone else is interested in working to develop a tutorial
    Ken> for matplotlib's OO API, please drop me a line... I have a
    Ken> vested interest in making matplotlib easier for busy
    Ken> developers to use.

I suggest extending Robert's tutorial linked here

  http://matplotlib.sourceforge.net/faq.html#OO

Thanks!
JDH

I mostly agree with Chris's comments about matplotlib and
Numeric/scipy, etc, and think that keeping the explicit
namespace hierarchy is useful.  If pylab.py added the line
    import matplotlib.numerix as NX

(or something similar) then you could do this
    import pylab as p
    x = p.NX.arange(100.0)
    y = p.NX.sin(2*nx.pi*x)
    p.plot(x,y)
    p.show()

If 'p.NX' seems too ugly, you could always do 
    import pylab as p
    N = p.NX
    x = N.arange(100.0)
    y = N.sin(2*nx.pi*x)
    p.plot(x,y)
    p.show()

That seems very easy to use and avoid namespace conflicts, and
still keeps the hierarchy obvious enough to track down where any
method originates from.

My 2c,

--Matt

On May 24, 2005, at 11:25 AM, Chris Barker wrote:
> John Hunter wrote:
>>     Chris> One way to get there is to add much of the functionality of
>>     Chris> pylab to the OO interface. I really wish I had the time to
>>     Chris> write an OO-pylab, I think it would be really great, even
>>     Chris> for interactive use.
>> I think the OO interface is already pretty easy to use.
>
> It may have gotten better. I haven't use it much recently, my main 
> matplotlib using project has been handed off to another coder. I just 
> remember that as much as I wanted to use the OO interface, It ended up 
> being much easier to use pylab.whatever much of the time. Maybe the 
> real problem isn't what's there, but what's in the examples.

I've found the OO interface to be very pleasant to use.  While learning 
matplotlib,  I translated a bunch of the pylab examples to the OO API 
(look at the plot_XYZ() functions):

	http://agni.phys.iit.edu/~kmcivor/potpourri/wxmpl-demos.py

>>   * Easier attribute setting (eg x.facecolor = 'r') but this is
>>     already accomplished somewhat since the set/get introspection
>>     facilities are now available in matplotlib.artist to the OO user
>
> I just looked in the class docs, and I still can't see how to set 
> something in an OO way, like the facecolor, for example:
>
> x.set('facecolor', 'r') maybe?
>
> I know I'd rather x.SetFaceColor('r') or something like that, but the 
> above is OK too.

I'm all for having more consistent accessors for the various object 
properties.  Perhaps something like this would work well?  (yeah, it's 
modeled on Tkinter's configure() method)

	# def set(cfgdict=None, **kwds) -> None
	x.set(facecolor='r', size=2)

> Maybe a good start would be to go through the tutorial and users 
> guide, and try to re-write all the examples in an OO manner, and see 
> what happens.

Feel free to use any of the examples in the file I've linked to 
above... they're all under the  matplotlib license, as they're derived 
from the matplotlib example scripts.

If anyone else is interested in working to develop a tutorial for 
matplotlib's OO API, please drop me a line... I have a vested interest 
in making matplotlib easier for busy developers to use.

Ken

>>>>> "Nicholas" == Nicholas Young <su...@su...> writes:

    Nicholas> There seems to be a bug somewhere in the CVS version of
    Nicholas> matplotlib or the 2.3 version of agg that's causing me
    Nicholas> sporadic segfaults.  It's possible this isn't general
    Nicholas> and is due to some other compiled code but doesn't seem
    Nicholas> particularly likely as the bug didn't appear when
    Nicholas> running with a copy of matplotlib from CVS on April 14.
    Nicholas> However, I've no idea what's causing but problem and
    Nicholas> this may be a coincidence.

Compile mpl with VERBOSE =  True in setup.py which will help inform
where the segfault is occurring.  You will want to rm -rf your build
dir to force a clean debug build.

JDH

There seems to be a bug somewhere in the CVS version of matplotlib or
the 2.3 version of agg that's causing me sporadic segfaults.  It's
possible this isn't general and is due to some other compiled code but
doesn't seem particularly likely as the bug didn't appear when running
with a copy of matplotlib from CVS on April 14.  However, I've no idea
what's causing but problem and this may be a coincidence.

I've made some attempt to track down the problem but failed (I don't
have a copy of Python installed with debugging compiled in and don't
have time to compile one).  I've attached the file containing the
plotting library; the calling code references the library as utils.plot
and is:

import utils.plot, Numeric
im = Numeric.zeros((2048,1952,4), Numeric.UInt8)
p = utils.plot.plot('n', modes=(1,11), xlabel="Time (s)",
ylabel="Frequency (kHz)")
p.imshow(im/255., interpolation="nearest")
p.show()

which on it's own runs fine.  Running the same code in the context of my
program (inserted in the place of the real data plotting code) and it
seems to crash on it's second run.  The other code loaded is f2py
wrapped Fortran which is using a fairly large amount of memory (at
minimum ~100MB and sometimes a lot more).

The reason I say seems is that if I insert print statements to check the
behaviour changes (and in fact goes away entirely sometimes); the
program never crashes on the first run.  It seems fairly likely that no
one is going to have a clue what's causing this but on the off chance
someone else is having the same problem I thought I'd ask.


Thanks for any help,
Nicholas Young

Hello, does anyone know how to move a y axis label so that it doesn't
cover up the y axis grid values? Thanks for the help!

Jeff