matplotlib-users Mailing List for matplotlib

>>>>> "Steve" == Steve Chaplin <ste...@ya...> writes:

    Steve> John, I noticed that when plotting sine waves
    Steve> (simple_plot.py for example) with the gtk backend that the
    Steve> lowest points are not plotted.

Hi Steve, thanks for letting me know.  There is an off-by-one error
and it looks like and easy fix.  For future reference, you may want to
consider using GTKAgg as your default GUI.  This has the GTK widget
but uses agg for rendering.  Agg supports subpixel rendering and so
isn't susceptible to one pixel errors that crop up in GTK in a number
of contexts.  At low resolutions, these become particularly
noticeable.  Other benefits over the GTK backend are alpha blending,
anti-aliased drawing, and faster image support -
http://matplotlib.sourceforge.net/backends.html#GTKAgg

    Steve> So I wrote a test script to plot a square, the result is
    Steve> that the left and top edges are plotted and the bottom and
    Steve> right edges are clipped off (I can pan the view to display
    Steve> the missing lines). I can't think of any reason why you
    Steve> would plot data points and then expect them to be clipped
    Steve> off, so to me it looks like an off-by-one error.

Now on to your problem.

In backend_gtk draw_rectangle, change

        x, y = int(x), self.height-int(math.ceil(y+height))

to
        x, y = int(x), self.height-int(y+height)

and the GraphicsContext.set_clip_rectangle method to

    def set_clip_rectangle(self, rectangle):
        GraphicsContextBase.set_clip_rectangle(self, rectangle)
        l,b,w,h = rectangle
        rectangle = (int(l), self.renderer.height-int(b+h)+1,
                     int(w), int(h))
        self.gdkGC.set_clip_rectangle(rectangle)        

This fixes the bug, but doesn't handle your test case.  The lines in
your example are still clipped, but there is a reason for that.  In
your example, the lines are exactly where the axes lines will be
drawn.  It's a judgment call whether you want to see the axes line or
your line at that location.  In interactive navigation when you pan
and zoom around, it often happens that your data extend beyond the
axes lines; in this case you usually want a clean axes line not
partially obscured by your data.

If I set the clip so that the lines in your example are plotted, then
the axes lines are also overridden in other where the data extend
beyond the axes.

By tweaking the clip rectangle, eg 

        rectangle = (int(l), self.renderer.height-int(b+h),
                     int(w+1), int(h+2))

you can get your lines drawn but then the axes lines are obscured, eg
in subplot_demo and arctest.

Try experimenting with a few different demos and clip settings to see
what you think is the best compromise; let me know.

In Agg this is less of a problem since agg uses pixel blending when
two pixels are drawn at the same location so the data pixel over the
axes line pixel is less glaring.

Cheers,
JDH

>>>>> "Greg" == Greg Whittier <gr...@th...> writes:

    Greg> As a temporary solution you might try just transforming your
    Greg> r,theta data to x, y and then drawing a grid over it.

A nice workaround.  You may want to add 

  axis('off')

To get rid of the background axes.
 
    Greg> I looked at the classes and with the loglog already done as
    Greg> an example, it shouldn't be too hard to add polar plotting.
    Greg> So far though I haven't got any further than printing out
    Greg> some of the code.

I was planning on taking a different tack, and derive a PolarAxes from
Axes and RadialAxis from Axis, etc, which uses circles rather then
lines for the radial gridlines, and so on. But you get so close with
so little code that your approach may be better.  If you want to keep
forging ahead, I'm happy to leave the ball in your court.

On an unrelated note,

  from Numeric import *
  from matplotlib.matlab import *

is redundant because matplotlib.matlab imports all of numeric/numarray
as well as MLab, fft, and some stuff from LinearAlgebra and Matrix.
This is to provide a matlab like environment where most of the things
you need are there.

JDH

John,
I noticed that when plotting sine waves (simple_plot.py for example)
with the gtk backend that the lowest points are not plotted.

So I wrote a test script to plot a square, the result is that the left
and top edges are plotted and the bottom and right edges are clipped off
(I can pan the view to display the missing lines). I can't think of any
reason why you would plot data points and then expect them to be clipped
off, so to me it looks like an off-by-one error.

Test program:

from matplotlib.matlab import *

figure(1)
x = arange(0, 10+1, 1)
plot(x,     x*0+10, 'r-',
     x,     x*0,    'r-',
     x*0,   x,      'r-',
     x*0+10, x,     'r-')

show()

Regards,
Steve

John Hunter wrote:

>>>>>>"LUK" == LUK ShunTim <shu...@po...> writes:
> 
> 
>     LUK> If matplotlib honours the HOME environmental variable, could
>     LUK> it not be used on windows system as well?
> 
> Could you provide the context for your question?  What are you trying
> to do and what isn't working?
> 
> JDH
> 

Hello John,

I'm sorry I was in a hurry to go home and tried to read my mail before 
that. I did not make myself clear. I just clicked on the link in the 
message to take a peek at the .matplotlibrc file and found that "On 
windows, this would be, for example, C:\Python23\share\matplotlib." That 
led me to wonder whether HOME will take effect in windows installation.

I had not updated matplotlib for a while and I know it has seen big 
improvements. I've now downloaded version 0.52 and I can see now when 
HOME is set, matplotlib will first read the config file there.

Perhaps the comments in the original .matplotlibrc can be altered to 
make this clear. It's a really a very good idea to be able to set 
everything using just one config file.

I'm sure the people on the list will agree that matplotlib is a great 
piece of work and you have been wonderful in answering questions.

Good day,
ST
--

As a temporary solution you might try just transforming your r,theta
data to x, y and then drawing a grid over it.

I looked at the classes and with the loglog already done as an example,
it shouldn't be too hard to add polar plotting.  So far though I haven't
got any further than printing out some of the code.

Here's a very rough example of a workaround.

#!/usr/bin/python
from Numeric import *
from matplotlib.matlab import *
 
def drawgrid(sp,rticlevels,thetaticlevels):
    for r in rticlevels:
        theta = arange(0,2*pi+0.05,0.05)
        x = r*cos(theta)
        y = r*sin(theta)
        sp.plot(x,y,'k-')
    for theta in thetaticlevels:
        x = rticlevels[-1]*cos(theta)
        y = rticlevels[-1]*sin(theta)
        sp.plot([0,x],[0,y],'k-')
 
def polar(sp,r,theta,marker,rticlevels,thetaticlevels):
    x = r*cos(theta)
    y = r*sin(theta)
    sp.plot(x,y,marker)
    drawgrid(sp,rticlevels,thetaticlevels)
    return sp
 
sp = subplot(111)
theta = arange(0,pi,0.1)
r = 0.5 + cos(theta)
polar(sp,r,theta,'b-',arange(0.5,2.0,0.5),arange(0.,2*pi,pi/9.))


On Tue, 2004-03-30 at 14:32, Peter Groszkowski wrote:
> Hello:
> 
> I am currently using matplotlib for all the plotting in the software I am writing. I will however need to produce polar plots. As John has mentioned they should be added at one point. So my shameless question is roughly what version could I expect them to be included in? My options are to either wait for it, write it on my own, or write a simple interface (for my code) to GNUPlot or some other tool. I have not done very much poking around in the current matplotlib libraries (other than changing some rather minor details) and have a feeling that this might take me the longest. Interfacing GNUPLot to my code would not take more than a few hours, but I would prefer to stay with matplotlib. 
> 
> Thanks for the great work.
> Best,

Hello:

I am currently using matplotlib for all the plotting in the software I am writing. I will however need to produce polar plots. As John has mentioned they should be added at one point. So my shameless question is roughly what version could I expect them to be included in? My options are to either wait for it, write it on my own, or write a simple interface (for my code) to GNUPlot or some other tool. I have not done very much poking around in the current matplotlib libraries (other than changing some rather minor details) and have a feeling that this might take me the longest. Interfacing GNUPLot to my code would not take more than a few hours, but I would prefer to stay with matplotlib. 

Thanks for the great work.
Best,

-- 
Peter Groszkowski         Gemini Observatory
Tel: +1 808 974-2509      670 N. A'ohoku Place
Fax: +1 808 935-9235      Hilo, Hawai'i 96720, USA

>>>>> "LUK" == LUK ShunTim <shu...@po...> writes:

    LUK> If matplotlib honours the HOME environmental variable, could
    LUK> it not be used on windows system as well?

Could you provide the context for your question?  What are you trying
to do and what isn't working?

JDH

    

John Hunter wrote:
>>>>>>"marc" == marc schellens <m_s...@ho...> writes:
> 
> 
> Hi Marc,
> 
>     marc> Just installed matplotlib and tried an example from the
> 
>     marc> Numeric import failed... trying numarray.  
> 
> This is not an error, but it looks like you have numarray installed
> but not Numeric, but you haven't set your numerix preference to
> numarray.  This is a parameter in .matplotlibrc. See
> http://matplotlib.sourceforge.net/.matplotlibrc.  If indeed you want
> to use numarray, I suggests setting
> 
> numerix      : numarray   
> 
> or else install Numeric.  This will stop the numeric/numarray
> warnings.
> 

If matplotlib honours the HOME environmental variable, could it not be used on 
windows system as well?

Regards,
ST
-- 

I just installed the latest matplotlib and wanted to run
the first example from the homepage.
But I got:

Python 2.3.3 (#2, Mar 12 2004, 16:09:39)
[GCC 3.2.2 (Mandrake Linux 9.1 3.2.2-3mdk)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
 >>> import matplotlib.matlab
Numeric import failed... trying numarray.
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
   File "/usr/local/lib/python2.3/site-packages/matplotlib/matlab.py", 
line 126, in ?
     from axes import Axes
   File "/usr/local/lib/python2.3/site-packages/matplotlib/axes.py", 
line 244, in ?
     class Axes(Artist):
   File "/usr/local/lib/python2.3/site-packages/matplotlib/axes.py", 
line 814, in Axe                                            s
     def imshow(self, X, cmap = Grayscale(256)):
   File "/usr/local/lib/python2.3/site-packages/matplotlib/colors.py", 
line 213, in _                                            _init__
     Colormap.__init__(self, N, 'gray')
   File "/usr/local/lib/python2.3/site-packages/matplotlib/colors.py", 
line 96, in __                                            init__
     self._make_red()
   File "/usr/local/lib/python2.3/site-packages/matplotlib/colors.py", 
line 118, in _                                            make_red
     self.red = 1.0/self.N*arange(self.N, typecode=Float)
TypeError: arange() got an unexpected keyword argument 'typecode'



Any suggestions?

thanks,
marc

Just installed matplotlib and tried an example from the homepage:

Python 2.3.3 (#2, Mar 12 2004, 16:09:39)
[GCC 3.2.2 (Mandrake Linux 9.1 3.2.2-3mdk)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>import matplotlib.matlab
Numeric import failed... trying numarray.
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/local/lib/python2.3/site-packages/matplotlib/matlab.py", line 
126, in ?
    from axes import Axes
  File "/usr/local/lib/python2.3/site-packages/matplotlib/axes.py", line 
244, in ?
    class Axes(Artist):
  File "/usr/local/lib/python2.3/site-packages/matplotlib/axes.py", line 
814, in Axe                                            s
    def imshow(self, X, cmap = Grayscale(256)):
  File "/usr/local/lib/python2.3/site-packages/matplotlib/colors.py", line 
213, in _                                            _init__
    Colormap.__init__(self, N, 'gray')
  File "/usr/local/lib/python2.3/site-packages/matplotlib/colors.py", line 
96, in __                                            init__
    self._make_red()
  File "/usr/local/lib/python2.3/site-packages/matplotlib/colors.py", line 
118, in _                                            make_red
    self.red = 1.0/self.N*arange(self.N, typecode=Float)
TypeError: arange() got an unexpected keyword argument 'typecode'

Why is this?
Any suggestions?

thanks,
marc

_________________________________________________________________
Add photos to your e-mail with MSN 8. Get 2 months FREE*. 
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Hi

Just a quick note that the EPS bounding box still seems to be buggy in 
matplotlib 0.52. 

If I save an EPS using the save button on a GTK figure window, the right
hand side gets slightly clipped when printed.

If I do the same from a TkAgg window, most of the plot gets clipped.

Cheers,
Matthew.

John,
Yes, I am using matplotlib from cvs. I'll join the devel list to make
sure I know what changes are happening.

I did notice that the CHANGELOG file is not up to date, which is a shame
as it prevents someone from diagnosing their own problems. I thought
that one of the benefits of cvs is that you can check in changes with a
changelog comment so that you know where to rollback a change if there
are unforeseen problems.

Steve

>>>>> "Steve" == Steve Chaplin <ste...@ya...> writes:

    Steve> John, I'm having a problem running the barchart demo, it
    Steve> reports:

    Steve> $ python barchart_demo.py Traceback (most recent call
    Steve> last): File "barchart_demo.py", line 23, in ?  legend(
    Steve> (p1[0], p2[0]), ('Men', 'Women') ) File
    Steve> "/usr/lib/python2.3/site-packages/matplotlib/matlab.py",
    Steve> line 765, in legend return gca().legend(*args, **kwargs)
    Steve> File "/usr/lib/python2.3/site-packages/matplotlib/axes.py",
    Steve> line 972, in legend self._legend = Legend(self.dpi,
    Steve> self.bbox, lines, labels, loc) File
    Steve> "/usr/lib/python2.3/site-packages/matplotlib/legend.py",
    Steve> line 104, in __init__ self._texts = self._get_texts(labels,
    Steve> textleft, upper) File
    Steve> "/usr/lib/python2.3/site-packages/matplotlib/legend.py",
    Steve> line 206, in _get_texts transy = self.transy, TypeError:
    Steve> __init__() got an unexpected keyword argument 'fontsize'

Hi Steve - you're running CVS right?

Font management is undergoing a thorough overhaul.  Paul Barrett has
written a free standing, platform independent, font-finder (no
ttfquery or FontTools dependency) and we're still working out the
bugs.  Basically, all the font dict and font kwargs examples are
currently broken in CVS, but Paul is aware of this and will probably
have it cleaned up in a couple of days.

The nice thing about the new design is it will enable specifying fonts
in a way that will work across backends and platforms using a naming
scheme and font finder algorithm that is based on the W3C Cascading
Style Sheet specification.  See the thread
http://sourceforge.net/mailarchive/message.php?msg_id=7544800.  

If you plan to work with the CVS version, I recommend subscribing to
the devel list so you can get a heads up on these issues.  Generally
we try to keep a working version in CVS, but if you on the bleeding
edge.....

JDH

John,
I'm having a problem running the barchart demo, it reports:

$ python barchart_demo.py
Traceback (most recent call last):
  File "barchart_demo.py", line 23, in ?
    legend( (p1[0], p2[0]), ('Men', 'Women') )
  File "/usr/lib/python2.3/site-packages/matplotlib/matlab.py", line
765, in legend
    return gca().legend(*args, **kwargs)
  File "/usr/lib/python2.3/site-packages/matplotlib/axes.py", line 972,
in legend
    self._legend = Legend(self.dpi, self.bbox, lines, labels, loc)
  File "/usr/lib/python2.3/site-packages/matplotlib/legend.py", line
104, in __init__
    self._texts = self._get_texts(labels, textleft, upper)
  File "/usr/lib/python2.3/site-packages/matplotlib/legend.py", line
206, in _get_texts
    transy = self.transy,
TypeError: __init__() got an unexpected keyword argument 'fontsize'

Regards,
Steve

>>>>> "Steve" == Steve Chaplin <ste...@ya...> writes:

    Steve> John, I'm having a problem with gridlines.  I set axes.grid
    Steve> : True in my .matplotlibrc file

    Steve> But when I run examples/embedding_in_gtk.py and
    Steve> examples/simple_plot.py there are no gridlines.


Oops, this was just an oversight.  In matplotlib.axes.Axes.cla, change


        self._gridOn = False
to 
        self._gridOn = rcParams['axes.grid']


Should help; thanks for letting me know,
JDH

John,
I'm having a problem with gridlines.
I set
axes.grid          : True
in my .matplotlibrc file

But when I run
examples/embedding_in_gtk.py and
examples/simple_plot.py there are no gridlines.

Regards,
Steve

>>>>> "paulo" == paulo  <phe...@eo...> writes:

    paulo> I am using the scatter plot of Matplotlib to plot the
    paulo> position of each particle. That works great, but when I try
    paulo> to assign different colors to each dot according to their
    paulo> concentration I find some problems. Although there is a big
    paulo> range of concentrations (colors) I can only see two in the
    paulo> plot. Is it possible to define more intervals to assign the
    paulo> colors?  I think I did not understand the right way to
    paulo> define the c array intensities when I use the command:
    paulo> scatter(self, x, y, s=None, c) How should I generate that
    paulo> array? I looked at the example but I couldn't figure it
    paulo> out.

Hi Paulo,

It would help to see some code to let you know why your current
approach isn't working.  For now, all I can say is that c should be a
len(x) Numeric array of concentrations.  It might help for you to do

  hist(c, 100) 

to look at the distribution of concentrations.  If the distribution is
bimodal and strongly peaked, this may explain why you only see two
colors.

As for your question about defining more colors, the default is to use
a colormap of 1000 colors, which should be an ample number to see a
range unless something funny is going on with your c array.

When you post some code, also post the first few entries of c, eg
c[:10].

JDH

>>>>> "Kirk" == Kirk Lamont <k.l...@us...> writes:

    Kirk> Hey.  We are using Matplotlib with Python and C to create
    Kirk> run time graphs.  However, we are having trouble figuring
    Kirk> out how to get the axes to show up in scientific notation.
    Kirk> If anyone have some info it would be very much appreciated.
    Kirk> Thanks

If I understand you correctly, you want to use notation like 1.0e-6 on
the x and/or y axis tick labels.  Is this correct?  Having more
automated tick labelers is something that has been discussed and will
be added in the not-too-distant future.

In the mean time you can control them directly

  ax = subplot(111)
  plot([1,2,3])
  xticks = ax.get_xticks()

  labels = [ '%1.0e'%val for val in xticks ]
  ax.set_xticklabels(labels)

or you may want to define your own ticks

  xticks = [1e-6, 2e-6, 3e-6, 4e-6]
  ax.set_xticks(xticks)
  labels = [ '%1.0e'%val for val in xticks ]
  ax.set_xticklabels(labels)

Hope this helps,
John Hunter

 

>>>>> "Engelsma," == Engelsma, Dave <D.E...@La...> writes:

    Engelsma,> Any ideas?

The following script, all negative data, works fine for me:

    from matplotlib.matlab import *

    x = randn(1000)-10
    hist(x, 10)
    show()

Make sure this example works for you (if not upgrade matplotlib), and
then go back to your example.  Take out all the customization stuff
after the call to

	n, bins, patches = matplotlib.matlab.hist(histogram_data, 10,
normed=0)

and see if that works.  If so, slowly add things back until you find
out what is wrong.  If it's a matplotlib error rather than an error on
your side, let me know.

JDH

Hello -

I'm creating a histogram with a negative data values (30 values between -1.5
and -0.5). The histogram is created, however the data is plotted as if the
values were forced positive (i.e. forced to absolute values).

I've checked exactly what data is being passed to the hist function and the
data goes in as a series of negative values.

The Python code:

	# Generate chart using matplotlib library
	histogram_data = array.array('f')
	histogram_data.fromlist(DimensionData)
	overall_range = max(DimensionData) - min(DimensionData)
	x_lowest = min(DimensionData) - (2*overall_range)
	x_highest = max(DimensionData) + (2*overall_range)

	# the histogram of the data
	n, bins, patches = matplotlib.matlab.hist(histogram_data, 10,
normed=0)
	histogram = matplotlib.matlab.subplot(111)

	# add a 'best fit' line
	y = matplotlib.mlab.normpdf(bins, SC.meanVal, SC.stdDev)
	lines = histogram.plot(bins, y, 'r-')
	for line in lines:
		line.set_linewidth(1)

	# plot lines on histogram indicating upper & lower control limits
along with 
	#   nominal dimension.
	histogram.set_xlim([x_lowest, x_highest])
	histogram.plot([SC.LCL,SC.LCL],[0,max(n)],'b--')
	histogram.plot([SC.Nom,SC.Nom],[0,max(n)],'g--')
	histogram.plot([SC.UCL,SC.UCL],[0,max(n)],'r--')

	# Set axis labels
	histogram.set_xlabel(DataDesc)
	histogram.set_ylabel('Number of Parts')

	# Setup strings for chart legend
	LegUCL = "UCL: " + str(SC.UCL)
	LegNom = "Nominal: " + str(SC.Nom)
	LegLCL = "LCL: " + str(SC.LCL)

	histogram.legend(["Curve", LegLCL, LegNom, LegUCL],fontsize = 10)
	histogram.set_xlim([x_lowest, x_highest])
	
	#matplotlib.matlab.savefig(filePath)
	matplotlib.matlab.show()
	matplotlib.matlab.close()

Any ideas?

Thanks in advance,

Dave Engelsma
Lacks Wheel Trim Systems

Hey.  We are using Matplotlib with Python and C to create run time
graphs.  However, we are having trouble figuring out how to get the axes
to show up in scientific notation.  If anyone have some info it would be
very much appreciated.  Thanks
 

Hi,
I am simulating the movement of some particles that carry some
concentration of different species. Those concentrations change in time
and space and I would like to be able to see their distribution in
space. 

I am using the scatter plot of Matplotlib to plot the position of each
particle. That works great, but when I try to assign different colors to
each dot according to their concentration I find some problems. Although
there is a big range of concentrations (colors) I can only see two in
the plot. Is it possible to define more intervals to assign the colors?
I think I did not understand the right way to define the c array
intensities when I use the command:  
scatter(self, x, y, s=None, c)
How should I generate that array? I looked at the example but I couldn't
figure it out.

Thanks for your help,
I look forward to see the future versions of Matplotlib. So far, it
looks very good.
Paulo.

Hi.

Chaco is also included in SciPy, which is a really interesting 
scientific computing package. And I do agree with Mr. Coelho that 
Matplotlib is more flexible (yet as far as I know, Chaco offers 3D 
plotting as well). Have you been in contact with the Scipy team?

Another idea.

See you
Vincent

Flavio Codeco Coelho wrote:

> HI everybody,
>
> I dont know if any of you is aware of the boa-constructor python IDE 
> and wx gui builder.
>
> I use it and subscribe to its mailing list. Recently, there was this 
> discussion about having some scientific plotting controls added to 
> Boa. I include below, a message from Boa's main developer, Ryaan 
> Booysen, where he gives some pointers to anyone that might be 
> interested in adding plotting controls to Boa. They are talking about 
> Chaco, but as far as I know, Chaco development is stalled and 
> Matplotlib is far superior (IMHO).
>
> I believe that if anyone is interested in doing that should contact 
> Ryaan. He is a very nice guy. I also believe that it would greatly 
> improve the visibility of matplotlib since Boa has a very large user base.
>
> Well, its just an idea.
>
> have fun
>
> Flavio
>
>
>
> -----Forwarded Message-----
>
>*From:* Riaan Booysen <riaan@e.co.za>
>*To:* Ricardo Henriques <pax...@sa...>
>*Cc:* boa...@li... <boa...@li...>
>*Subject:* Re: [Boa Constr] Fw: Any Chaco plugins?
>*Date:* Tue, 09 Mar 2004 13:33:00 +0200
>
>Hi Ricardo,
>
>Ricardo Henriques wrote:
>> Hi...
>> I sucessfully used Boa to help me build scientific applications. I normally
>> use wxPyPlot to plot graphics witch has a plug-in for Boa, it is quite
>> alright, but sometimes I nead a plotting library with more features like
>> Chaco found at _www.scipy.org_ <http://www.scipy.org> . Anyone knows any plug-in for this plotting
>> library or any other than wxPyPlot?
>> Where can I get some information about how to build a plug-in for Boa? 
>> Tks...
>
>You may look at the examples for adding a control in
>Plug-ins/UserCompanions.py
>
>I suggest you first try to use the Custom Classes feature to
>use a Chaco Plot window in the Designer.
>See Docs/boa/apphelp/MixingSource.html
>This might be a simpler option.
>
>Cheers,
>Riaan.
>
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I had a look at backend_gtk.py and noticed that the toolbar code
could be simplified.

Instead of
        iconw = gtk.Image()
        iconw.set_from_stock(gtk.STOCK_GO_BACK, iconSize)

you could do two steps in one with
        iconw = gtk.image_new_from_stock(gtk.STOCK_GO_BACK, iconSize) 

The pygtk Changelog says that gtk.image_new_from_stock() has been
available since 1.99.5.

Regards
Steve

S=E6l !

Thanks for the tip, but I do not want to use the lagrangian: I want many sm=
all polynoms, not 1

What I want to do is very typical in Finite Element Method eventhough this =
is not the case here.
I just want to define many small polynoms between consecutives points.
Each one is stsifying the continuity of the value as well as the derivative
if I define my function as f(x)=3Dax*x+bx+c
At my points (X0,Y0) (X1,Y1) as well at teh derivative a X0 to be Z0 I get =
the follwoing
f(X0)=3DY0=3Da*X0*X0+b*X0+c
f(X1)=3DY1=3Da*X1*X1+b*X1+c
f'(X0)=3DZ0=3D 2aX0+b

After small manipulkation I can directly infere a,b,c

This is a very simple but useful routine that I was hoping people would hav=
e already written
Actually it is much smoother with a cubic polynomial, but it is a bit more =
complicated to implement

Thanks anyway

Jean-Baptiste



On Fri, 19 Mar 2004 23:49:28 +1000
"Gary Ruben" <ga...@em...> wrote:

> First, let me say, I don't know if there is code to do exactly what you w=
ant but here are my thoughts.
> It sounds to me like you're asking for Lagrange polynomial fitting routin=
es. Googling for "lagrange polynomial python" does return some code here: <=
http://www.stanford.edu/~sturdza/akimamod/akimamod.py>
> Another possibility is the spline fitting routines in Scipy (scipy.interp=
olate). These may be appropriate if what you're really after is just a way =
to fit smooth functions through points. I've used the splrep and splev func=
tions there successfully to fit spline functions through points. When I was=
 looking for curve fitting routines recently, I also came across some more =
generalized curve fitting modules for Python but I can't recall where :-( I=
 think they were SWIG wrappers for a C library.
> Also, look at this:
> <http://www.scipy.org/site_content/remap?rmurl=3Dhttp%3A//www.scipy.net/p=
ipermail/scipy-user/2003-August/001864.html>
> HTH,
> regards,
> Gary
>=20
> ----- Original Message -----
> From: Jean-Baptiste Cazier <Jea...@de...>
> Date: Fri, 19 Mar 2004 11:49:21 +0000
> To: "Gary Ruben" <ga...@em...>, jdh...@ni...
> Subject: Re: [Matplotlib-users] Polyfit
>=20
> >=20
> > Thanks to both of you. It worked just fine
> >=20
> > I will push my luck and ask if any of you knows of a module to fit a pi=
ecewise polynomial to a list of (X,Y) points.
> > something like=20
> > p=3Dpiece-wiseFit([1,2,5,7,8],[3,4,2,5,5],2)=20
> > would return [[A0,B0,C0],[A1,B1,C1}[A2,B2,C2},[A3,B3,C3]}, coefficients=
 for the 4 polynoms=20
> > A0+B0.X+C0.X.X
> > A1+B1.X+C1.X.X
> > A2+B2.X+C2.X.X
> > A3+B2.X+C3.X.X
> >=20
> > This is a classic and I expect the code to be written somewhere, eventh=
ough I could not find it even when I "Feel lucky" with Google.
> <snip>
> --=20
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>=20


--=20
-----------------------------
Jea...@de...

Department of Statistics
deCODE genetics     Sturlugata,8
570 2993          101 Reykjav=EDk