Mailman 3 May 2005 - SciPy-User

Help required regding Eigenvectors
by Sudheer Phani 14 Mar '22

14 Mar '22

Hello All, I have been encountering some strange problems with the calculation of eigen vectors using python. The problem is with the sign of the eigen vectors calculated. On Very few occasions the eigen vectors calculated using python have an opposite sign than the actual eigenvectors, though the magnitude is correct. Can any one of you plz help me in this regard and suggest me some solution if you have encoutered similar problems . Any help in this regd is appreciated Thanks in Advace regds Sudheer

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(no subject)
by aurelien.gourrier＠free.fr 31 May '05

31 May '05

Hello, I would need some help or advice on the following point : I'm trying to fit some X-ray scattering data with either gaussian or lorentzian functions using the least square algorithm (optimize.leastsq). I started with something quite simple, i.e. defining the residuals for the different functions in a similar way as in the tutorial and then calling the leastsq routine. In the end, I find the results a bit puzzling : if I define the data to be fitted as a gaussian + random noise (as in the tutorial), the fit with gaussian functions is perfect. The fit of the same data with lorentzian is not very good, I have the impression that the fit position is quite OK and the integrated intensity as well, but the maximum intensity is way off... If I use real data where I have two peaks and linear background, as in the example below, then I simply cannot get correct fit, no matter how good the initial estimates are... Can anyone give me a bit of light on this one ? Many thanks Aure def multifuncresiduals(multifunc,y,x,gaunum=2,lornum=0,linenum=0): err = y for i in range(gaunum): #gaussian params come first in list print multifunc[2*i],multifunc[2*i+1] err = err-1/(sqrt(2*pi)*multifunc[2*i+1])*\ exp(-(x-multifunc[2*i])**2/(2*multifunc[2*i+1]**2)) for i in range(lornum): #lorentzian params come first in list i += gaunum #need to correct for index print multifunc[2*i],multifunc[2*i+1] err = err-1/pi*0.5*multifunc[2*i+1]/((x-multifunc[2*i])**2+(0.5*multifunc[2*i+1])**2) for i in range(linenum): i += gaunum + lornum #need to correct for index print multifunc[2*i],multifunc[2*i+1] err = err-(multifunc[2*i+1]+multifunc[2*i]*x) print '----------------' return err def multifunc(y,x,multifuncinit): result = leastsq(multifuncresiduals,multifuncinit,args=(y,x)) return result if __name__ == '__main__': ######################################## #test for multiple gaussian fit based on input file # #read chiplot file content datafilename = 'D:/Boulot/Software/Python/azimuth.chi' x,y =readChi(datafilename) #define init values multigauinit = [90,100,270,100] #initial estimates result= multifunc(y,x,multigauinit)

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Is it reasonable to ignore a "mild looking" FAILED scipy.test?
by robidoux＠cs.laurentian.ca 26 May '05

26 May '05

Scipy virgin here: Is it reasonable to ignore a "mild looking" FAILED scipy.test and get on with learning to use scipy? The story: After fairly careful linux install, scipy.test(level=1,verbosity=2) gives >>>>>BEGIN OUTPUT ... [snip] FAIL: check_cdf (scipy.stats.distributions.test_distributions.test_fatiguelife) ---------------------------------------------------------------------- Traceback (most recent call last): File "<string>", line 10, in check_cdf AssertionError: D = 0.362327598842; pval = 0.000245540127335; alpha = 0.01 args = (1.0213303917789236,) ---------------------------------------------------------------------- Ran 743 tests in 5.665s FAILED (failures=1, errors=15) <unittest.TextTestRunner object at 0x4053998c> <<<<<OUTPUT END All the errrors except one have to do with special functions (including orthogonal polynomials). ---- A related question: several packages had no test found, for example, >>>>>BEGIN OUTPUT !! No test file 'test_quadpack.py' found for <module 'scipy.integrate.quadpack' from '...s/scipy/integrate/quadpack.pyc'> <<<<<OUTPUT END (I picked this missing test file example B/C I am planning to use quadpack a lot.) Thank you for your patience, -- Nicolas Robidoux Departement de mathematiques et d'informatique Universite Laurentienne

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plt multiple plots?
by Rolf Wester 25 May '05

25 May '05

Hi, I would like to use plt to make multiple plots in one window and/or in multiple windows. I couldn't find anything about this in the docs. I would be very appreciative for any help on this problem. Thank you in anticipation Regards Rolf Wester

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Scipy and Python 2.4a3
by daniel＠rozengardt.net 24 May '05

24 May '05

Hello I´m newbie with scipy. I am working with Python 2.4a3 in Windows XP enviroment. I couldn´t install scipy because it seems to work only with Python 2.3. Any help about it? Thanks in advance Daniel Rozengardt

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Help on polar plot
by Rosa Ruiloba 24 May '05

24 May '05

Hello, I'm plotting vectors using gplt.polar function.I want to know if it's possible to plot several curves in the same plot with a command different than: polar(theta1,rho1,theta2,rho2) Is it possible to add a polar curve in an existing polar plot? Thank you, Rosa -- -- NOVELTIS Parc Technologique du Canal 2, avenue de l'Europe 31526 RAMONVILLE SAINT AGNE CEDEX Tel: +(33) (0)5.62.88.11.23

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Help on polar plot
by Rosa Ruiloba 24 May '05

24 May '05

Hello, I'm plotting vectors using gplt.polar function.I want to know if it's possible to plot several curves in the same plot with command a different than: polar(theta1,rho1,theta2,rho2) Is it possible to add a polar curve in an existing polar plot? Thank you, Rosa -- -- NOVELTIS Parc Technologique du Canal 2, avenue de l'Europe 31526 RAMONVILLE SAINT AGNE CEDEX Tel: +(33) (0)5.62.88.11.23

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Re: [AstroPy] Re: gui/thread issues
by Perry Greenfield 23 May '05

23 May '05

On May 23, 2005, at 2:03 PM, David King wrote: > > In the short run, I would be ok just using Tk alone on IPython or plain > Python, although I'd be happiest having the whole picture. In the > long run, > our project will want to serve varied users, who will no doubt want to > use > python in their own way. > Note that Tkinter windows under the standard Python interpreter are only 'alive' when the intepreter prompt is active. If you invoke a function that takes a long time, the window will be unresponsive since the Tk events are only handled within the Python interpreter loop. In this respect IPython should have an advantage with threading. > > I will continue to study what I have (that forum-thread link was > helpful > too--thanks). But I can't help feeling other python gui programmers > must > run up against this problem too, and wonder why practically all the > standard > Tkinter doc (including Grayson's book) just says "you gotta call > mainloop() > to make anything actually appear and respond in Tkinter" (manifestly > untrue). I think the problem is that, by and large, almost all uses of GUIs are centered on their being standalone applications and thus little thought is given to having a command line coexisting with the GUI. Our needs are pretty atypical in this regard. Perry Greenfield

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Error in 2D interpolation
by Nadav Horesh 22 May '05

22 May '05

I am getting errors using interpolate.bisplrep function. I've followed the scipy tutorial on 2D interpolation (page 23) and have the following piece of code: . . . old_x, old_y = N.mgrid[boundries[2]:boundries[3]:1j*mat.shape[0], boundries[0]:boundries[2]:1j*mat.shape[1]] print old_x.shape, old_y.shape, mat.shape tck = interpolate.bisplrep(old_x, old_y, mat, s=0) . . . generates the following error: (59, 127) (59, 127) (59, 127) # <== The output of the above print statement iopt,kx,ky,m= 0 3 3 7493 nxest,nyest,nmax= 152 152 152 lwrk1,lwrk2,kwrk= 22908510 13011569 28518 xb,xe,yb,ye= 0.000182 0.011776 0.002325 0.000182 eps,s 1.E-16 0. Traceback (most recent call last): File "process_mats.py", line 81, in ? interpolated = same_grid_interpolation(expanded, boundries, coord, 0.00008) File "process_mats.py", line 68, in same_grid_interpolation tck = interpolate.bisplrep(old_x, old_y, mat, s=0) File "/usr/local/lib/python2.4/site-packages/scipy/interpolate/fitpack.py", line 611, in bisplrep tx,ty,nxest,nyest,wrk,lwrk1,lwrk2) SystemError: error return without exception set System: Dual P4 PC + 512MB Gentoo linux (kernel 2.6.9) Python 2.4.1 scipy version 0.3.2_300.4521 Numeric 24.0 In another system I get MemoryError exception in the same place. The system is P3 + 192MB Gentoo linux (Kernel 2.4.20) Python 2.4.1 Numeric 23.7 Latest scipy from CVS. Any ideas? Nadav.

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conj and element-by-element multiplication
by Ryan Krauss 21 May '05

21 May '05

This is really more of a NumPy question, but I was calculating coherence and I need to multiply a vector by its own complex conjugate element-by-element. This should return a vector of real numbers in my mind, but instead returns a vector with imaginary parts identically equal to zero. Now maybe I have been spoiled by Matlab, but I ended up having to test that the imaginary parts really are 0 and then just kept the real part. Should this happen automatically, or am I just being a lazier whiner? Ryan

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