gnuplot-py-users Mailing List for Gnuplot.py

Ido Yehieli wrote:

>Hello,
>   is it possible to use gnuplot's 'fit' command
>throw Gnuplot.py?
>  
>

As the others have pointed out, you can call any gnuplot command from 
Gnuplot.py.  The other issue with "fit", however, is how do you get the 
results of the fit back into Python?  This is a problem because 
Gnuplot.py doesn't have access to gnuplot's standard output.

Luckily this is easy--you write the parameters to a "parameters file" 
(which fortuitously is valid python code) then read them back into 
python.  This is untested but should approximately work:

 >>> g = Gnuplot.Gnuplot()
 >>> open('fit.par', 'w').write('m=0\nb=0\n')
 >>> g('fit m*x+b "data.in" via "fit.par"')
 >>> g('update "fit.par" "fit2.par"') # saves fitted parameters to fit2.par
 >>> parameters = {}
 >>> execfile('fit2.par', globals(), parameters)
 >>> print parameters
{'b': 1.5015, 'm': 1e-30}
 >>> print parameters['m'], parameters['b']
1e-30 1.5015

In principle you could also parse "fit.log" to get the gory details 
about the fit (standard errors, correlation matrix, etc).

Hope this helps,
Michael

-- 
Michael Haggerty
mh...@al...

Hi Ido

> Hello,
>    is it possible to use gnuplot's 'fit' command
> throw Gnuplot.py?

Yes, my favorite feature in gnuplot is that you can
use ANY gnuplot command:

    g = Gnuplot.Gnuplot(debug=1)
    g('set data style lines')
    g('set logscale xy')
    g('set logscale x2')

Etc.

What I do is to use a combination of Gnuplot methods and
simple gnuplot calls like I showed in the example

Hope this helps,
-- Leo

Hello,
   is it possible to use gnuplot's 'fit' command
throw Gnuplot.py?

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Hello,

I don't use Windows, so I won't be of much help.  Therefore, I am 
forwarding your question to the gnuplot-users mailing list, where 
several windows users are subscribed and might have ideas.

It sounds vaguely like the gnuplot program was never started.  One thing 
appears incorrect in your attempt:

> I also tried to type:
> Gnuplot.GnuplotOpts.gnuplot_command = "C:\Programmi\gp373w32\pgnuplot"


Because of Python's treatment of backslashes in strings, I think you 
want to type either

Gnuplot.GnuplotOpts.gnuplot_command = "C:\\Programmi\\gp373w32\\pgnuplot"

or


Gnuplot.GnuplotOpts.gnuplot_command = r"C:\Programmi\gp373w32\pgnuplot"


Maybe that will help.

Michael

Giorgio Fagiolo wrote:

>Dear Michael: I've just successfully completed the installation of
>Gnuplot.py on a machine running Windows XP Home. I followed all your
>instuctions but something seems not working properly. In particular, I've
>been trying to type the following lines (in the Pythonwin interactive
>window):
>
>  
>
>>>>import Gnuplot
>>>>import Gnuplot.funcutils
>>>>g = Gnuplot.Gnuplot(debug=1)
>>>>g.plot([[0,1.1], [1,5.8], [2,3.3], [3,4.2]])
>>>>        
>>>>
>
>But then it gives me the following:
>
>Traceback (most recent call last):
>  File "<interactive input>", line 1, in ?
>  File "c:\python22\Lib\site-packages\Gnuplot\_Gnuplot.py", line 281, in
>plot
>    self.refresh()
>  File "c:\python22\Lib\site-packages\Gnuplot\_Gnuplot.py", line 222, in
>refresh
>    self(self.plotcmd + ' ' + string.join(plotcmds, ', '))
>  File "c:\python22\Lib\site-packages\Gnuplot\_Gnuplot.py", line 206, in
>__call__
>    self.gnuplot(s)
>  File "c:\python22\Lib\site-packages\Gnuplot\gp_win32.py", line 122, in
>__call__
>    self.write(s + '\n')
>IOError: [Errno 22] Invalid argument
>
>Just to give you more info: I have Gnuplot.py correctly installed under
>C:\Python22\Lib\site-packages\Gnuplot while GnuPlot (windows version
>including pgnuplot.exe) is installed under C:\Programmi\gp373w32.
>
>I also tried to type:
>Gnuplot.GnuplotOpts.gnuplot_command = "C:\Programmi\gp373w32\pgnuplot"
>but it does not work.
>Could you possibly help me out with this problem? Thanks in advance,
>Giorgio Fagiolo
>
-- 
Michael Haggerty
mh...@al...