matplotlib-users Mailing List for matplotlib

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Alan,

Thanks for the help.  This was a big clue.  It turns out that what I
thought was an array of arrays was actually a list of arrays.  If my
list was y, running plot(x,array(y).transpose()) solved the problem!

Thanks for your help,
Dave

Alan G Isaac wrote:
> On Mon, 01 Oct 2007, David D Clark apparently wrote:
>> y=[array([<f(x0)>]),array([<f(x1)>]),array([<f(x2)>])...] 
>> and x=array([x0,x1,x2,...])
> 
>> I want to plot the family of curves y=f(x). 
>> plot(x,y[n]) where n is the nth array in y plots the correct curve, 
>> however plot(x,y) and plot(x,y[:]) complain about mismatched array 
>> dimensions. 
> 
> 
> Might you want
> plot(x,y.transpose())
> 
> hth,
> Alan Isaac
> 
> 
> 
> 
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- --
David D. Clark
Electrical Engineer
P-23, Neutron Science and Technology
e-mail mailto:dd...@la...
GPG Public key 0x018D6523 available at http://pgp.mit.edu
http://www.gnupg.org has information about public key cryptography
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John Hunter wrote:
> On 10/2/07, Lars Friedrich <lfr...@im...> wrote:
>> Hello all,
>>
>> I am using matplotlib.mlab.psd to find power spectra of measured data.
>> Sometimes it happens that I use the automatic zero padding (if the
>> length of my measured data is smaller than nFFT) and detrending
>> (pylab.detrend_mean) at the same time.
>>
>> I think that the psd-algorithm does the zero padding *first* and *then*
>> uses the detrend function.
>>
>> For my application this is not good because it introduces low-frequency
>> signals that I can see in the spectrum. So the detrending does not work
>> as good as it does when there is no zero padding.
>>
>> What is the reason for this order of applying zero padding and
>> detrending? Wouldn't it make sense to change it?
> 
> I wrote this function many years ago and do not remember why I choose
> the order pad then detrend, but what you propose makes sense, so let's
> let this percolate for a bit and if noone objects I will change it
> (and related functions).

The change makes sense to me also.

Eric

On 10/2/07, Lars Friedrich <lfr...@im...> wrote:
> Hello all,
>
> I am using matplotlib.mlab.psd to find power spectra of measured data.
> Sometimes it happens that I use the automatic zero padding (if the
> length of my measured data is smaller than nFFT) and detrending
> (pylab.detrend_mean) at the same time.
>
> I think that the psd-algorithm does the zero padding *first* and *then*
> uses the detrend function.
>
> For my application this is not good because it introduces low-frequency
> signals that I can see in the spectrum. So the detrending does not work
> as good as it does when there is no zero padding.
>
> What is the reason for this order of applying zero padding and
> detrending? Wouldn't it make sense to change it?

I wrote this function many years ago and do not remember why I choose
the order pad then detrend, but what you propose makes sense, so let's
let this percolate for a bit and if noone objects I will change it
(and related functions).

JDH

Hello all,

I am using matplotlib.mlab.psd to find power spectra of measured data. 
Sometimes it happens that I use the automatic zero padding (if the 
length of my measured data is smaller than nFFT) and detrending 
(pylab.detrend_mean) at the same time.

I think that the psd-algorithm does the zero padding *first* and *then* 
uses the detrend function.

For my application this is not good because it introduces low-frequency 
signals that I can see in the spectrum. So the detrending does not work 
as good as it does when there is no zero padding.

What is the reason for this order of applying zero padding and 
detrending? Wouldn't it make sense to change it?

Thanks
Lars

-- 
Dipl.-Ing. Lars Friedrich

Photonic Measurement Technology
Department of Microsystems Engineering -- IMTEK
University of Freiburg
Georges-Köhler-Allee 102
D-79110 Freiburg
Germany

phone: +49-761-203-7531
fax:   +49-761-203-7537
room:  01 088
email: lfr...@im...

Daniel O'Connor wrote:
> Hi,
> I am trying to use matplotlib non-interactively but if I don't have
> DISPLAY set then wx barfs even though I have tried forcing the backend,
> etc..

This is characteristic of matplotlib that I think should be considered a 
major bug, but I have not gotten around to fixing it: you have to call 
matplotlib.use() *before* importing pylab for it to have any effect.  If 
you call it after the first import of pylab, it is silently ineffective, 
hence highly misleading. Many people are caught by this "gotcha".

I will fix this shortly by making matplotlib.use() raise an exception if 
matplotlib.backends has already been loaded.

Eric

> 
> eg..
> [midget 16:51] ~/projects/beermon >python
> Python 2.5.1 (r251:54863, Aug 14 2007, 11:27:14)
> [GCC 3.4.6 [FreeBSD] 20060305] on freebsd6
> Type "help", "copyright", "credits" or "license" for more information.
>>>> import pylab, matplotlib
> matplotlib.use>>> matplotlib.use('agg')
>>>> fig = pylab.figure()
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
>   File "/usr/local/lib/python2.5/site-packages/matplotlib/pylab.py", line 859, in figure
>     figManager = new_figure_manager(num, figsize=figsize, dpi=dpi, facecolor=facecolor, edgecolor=edgecolor, frameon=frameon, FigureClass=FigureClass, **kwargs)
>   File "/usr/local/lib/python2.5/site-packages/matplotlib/backends/backend_wxagg.py", line 134, in new_figure_manager
>     backend_wx.wxapp = wx.PySimpleApp()
>   File "/usr/local/lib/python2.5/site-packages/wx-2.6-gtk2-unicode/wx/_core.py", line 7791, in __init__
>     wx.App.__init__(self, redirect, filename, useBestVisual, clearSigInt)
>   File "/usr/local/lib/python2.5/site-packages/wx-2.6-gtk2-unicode/wx/_core.py", line 7700, in __init__
>     self._BootstrapApp()
>   File "/usr/local/lib/python2.5/site-packages/wx-2.6-gtk2-unicode/wx/_core.py", line 7352, in _BootstrapApp
>     return _core_.PyApp__BootstrapApp(*args, **kwargs)
> SystemError: wxEntryStart failed, unable to initialize wxWidgets!  (Is DISPLAY set properly?)
> 
> Same problem if I try Cairo.
> I had a google but no luck, can anyone help me out?
> 
> Thanks.
> 
> 
> 
> ------------------------------------------------------------------------
> 
> -------------------------------------------------------------------------
> This SF.net email is sponsored by: Microsoft
> Defy all challenges. Microsoft(R) Visual Studio 2005.
> http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users

On Tue, 2 Oct 2007, Jouni K. Sepp=E4nen wrote:
> "Daniel O'Connor" <da...@do...> writes:
> > I am trying to use matplotlib non-interactively but if I don't have
> > DISPLAY set then wx barfs even though I have tried forcing the
> > backend, etc..
>
> This should probably be in the FAQ... you need to set the backend
> before you import pylab, because importing pylab reads your
> matplotlibrc file and does all sorts of setup:
>
> import matplotlib
> matplotlib.use('agg')
> import pylab

Ahah, thanks - works much better now, I wondered why I couldn't affect=20
the backend :)

In the FAQ would be very nice!

PS thanks to all the devs for matplotlib, it is very useful!

=2D-=20
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C

"Daniel O'Connor" <da...@do...> writes:

> I am trying to use matplotlib non-interactively but if I don't have
> DISPLAY set then wx barfs even though I have tried forcing the backend,
> etc..

This should probably be in the FAQ... you need to set the backend before
you import pylab, because importing pylab reads your matplotlibrc file
and does all sorts of setup:

import matplotlib
matplotlib.use('agg')
import pylab

-- 
Jouni K. Seppänen
http://www.iki.fi/jks

Wayne E. Harlan wrote:
> I have a serious problem with my Linux installation of matplotlib.  It 
> segfaults after a very brief display of a plot window outline (no actual 
> plot within it).  Before presenting the details of my problem, I would 

If a straightforward plotting sequence, such as one of the examples, 
does this, then it sounds like a broken installation, not a matplotlib bug.

> like to download the latest CVS version to make sure this hasn't been 
> fixed already, however I cannot find any references to CVS in any of the 
> Matplotlib web pages, except for a reference for it in one of the recent 
> emails in this list.  How do I find it ?

See the following:

http://sourceforge.net/svn/?group_id=80706

We are using subversion, not cvs.

Eric

> 
> Thanks in advance,
> 
> Wayne

Hi,
I am trying to use matplotlib non-interactively but if I don't have
DISPLAY set then wx barfs even though I have tried forcing the backend,
etc..

eg..
[midget 16:51] ~/projects/beermon >python
Python 2.5.1 (r251:54863, Aug 14 2007, 11:27:14)
[GCC 3.4.6 [FreeBSD] 20060305] on freebsd6
Type "help", "copyright", "credits" or "license" for more information.
>>> import pylab, matplotlib
matplotlib.use>>> matplotlib.use('agg')
>>> fig =3D pylab.figure()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.5/site-packages/matplotlib/pylab.py", line 8=
59, in figure
    figManager =3D new_figure_manager(num, figsize=3Dfigsize, dpi=3Ddpi, fa=
cecolor=3Dfacecolor, edgecolor=3Dedgecolor, frameon=3Dframeon, FigureClass=
=3DFigureClass, **kwargs)
  File "/usr/local/lib/python2.5/site-packages/matplotlib/backends/backend_=
wxagg.py", line 134, in new_figure_manager
    backend_wx.wxapp =3D wx.PySimpleApp()
  File "/usr/local/lib/python2.5/site-packages/wx-2.6-gtk2-unicode/wx/_core=
=2Epy", line 7791, in __init__
    wx.App.__init__(self, redirect, filename, useBestVisual, clearSigInt)
  File "/usr/local/lib/python2.5/site-packages/wx-2.6-gtk2-unicode/wx/_core=
=2Epy", line 7700, in __init__
    self._BootstrapApp()
  File "/usr/local/lib/python2.5/site-packages/wx-2.6-gtk2-unicode/wx/_core=
=2Epy", line 7352, in _BootstrapApp
    return _core_.PyApp__BootstrapApp(*args, **kwargs)
SystemError: wxEntryStart failed, unable to initialize wxWidgets!  (Is DISP=
LAY set properly?)

Same problem if I try Cairo.
I had a google but no luck, can anyone help me out?

Thanks.

=2D-=20
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C

"Wayne E. Harlan" <wh...@pa...> writes:

> I cannot find any references to CVS in any of the Matplotlib web pages

The code is in a Subversion repository:

http://sourceforge.net/svn/?group_id=80706

(You probably want to add "/trunk" to the URL as mentioned in the
"warning" paragraph.)

> It segfaults after a very brief display of a plot window outline (no
> actual plot within it).

There are some instructions for debugging segfaults in the SEGFAULTS
file.

-- 
Jouni K. Seppänen
http://www.iki.fi/jks

I have a serious problem with my Linux installation of matplotlib.  It 
segfaults after a very brief display of a plot window outline (no actual 
plot within it).  Before presenting the details of my problem, I would 
like to download the latest CVS version to make sure this hasn't been 
fixed already, however I cannot find any references to CVS in any of the 
Matplotlib web pages, except for a reference for it in one of the recent 
emails in this list.  How do I find it ?

Thanks in advance,

Wayne

On Mon, 01 Oct 2007, David D Clark apparently wrote:
> y=[array([<f(x0)>]),array([<f(x1)>]),array([<f(x2)>])...] 
> and x=array([x0,x1,x2,...])

> I want to plot the family of curves y=f(x). 
> plot(x,y[n]) where n is the nth array in y plots the correct curve, 
> however plot(x,y) and plot(x,y[:]) complain about mismatched array 
> dimensions. 


Might you want
plot(x,y.transpose())

hth,
Alan Isaac