Mailman 3 August 2008 - 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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3D plotting
by Robert Cimrman 10 Sep '09

10 Sep '09

Hi, I need to do some simple 3D plots, so I tried the two Cookbook recipes (xplt, mplot3d) and failed: * xplt: does not work when using a custom installation directory such as python setup.py install --root=/home/share/software apparently the gistdata directory path is wrong: gist.error: failed to create drawing -- Gist work.gs style sheet missing * mplot3d: does not work with my version of matplotlib (0.80). I have made the changes mentioned in the Cookbook to no avail. (Axes.__init__() args apparently changed, as well as some other matplotlib object attributes) Any ideas? mplot3d looks great, I would really like to use it! thanks, r.

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assign to diagonal values?
by Carlos Scheidegger 07 Jul '09

07 Jul '09

Say I have a matrix m whose diagonal values I want to replace with the contents of vector new_diagonal. Right now, I'm using m -= diag(m) m += diag(new_diagonal) but that seems pretty wasteful (especially if diag() creates new arrays, which I suspect it does). Is there a standard (or any efficient) way to assign the diagonal values directly without an explicit for loop? Googling for "site:www.scipy.org assign diagonal" only returned results for sparse matrices, which is not the case here - these are plain numpy arrays. Thanks in advance, -carlos

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Is numpy's argsort lying about its numpy.int32 types?
by Rob Clewley 15 May '09

15 May '09

Hi, I'm having a problem comparing some types when using numpy's argsort. I'm using numpy 1.0.2. I can reproduce it simply: Python 2.4.4 (#71, Oct 18 2006, 08:34:43) [MSC v.1310 32 bit (Intel)] << snip >> In [1]: from numpy import argsort, sort, int32, array In [2]: x=array([1,3,2]) In [3]: aa=argsort(x) In [4]: as=sort(x) In [5]: type(aa[0]) Out[5]: <type 'numpy.int32'> In [6]: type(as[0]) Out[6]: <type 'numpy.int32'> In [7]: int32 Out[7]: <type 'numpy.int32'> In [8]: type(as[0])==int32 Out[8]: True In [9]: type(aa[0])==int32 Out[9]: False Any of the three indices in aa give me the same problem. Can someone explain if I should be doing this a different way, and if this is a bug?! Thanks, Rob

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signal.lti(A,B,C,D) with D=0
by William Purcell 18 Feb '09

18 Feb '09

I am trying to set up state space representation of a system using signal.lti. The system has no feedforward so D = 0. I've tried the three options listed in the code below to represent D. The only way I can get it to work is option 2 if C has 1 row. If C has more than 1 row it won't work. Any thoughts? -Bill Code --------------------------------------------------------------- from numpy import ones,matrix from scipy import signal r = ones(3) A = matrix([r,r,r]) B = matrix([r]).T C = matrix([r,r]) #three options of D to make it 0 #1) D=0 #2) D = matrix([0,0]).T #3) D = None D = 0 #D = None #D = matrix([0,0]).T Gss = signal.lti(A,B,C,D) ----------------------------------------------------------- Tracebacks ----------------------------------------------------------- Option 1 /usr/lib/python2.5/site-packages/scipy/signal/ltisys.py in abcd_normalize(A, B, C, D) 101 raise ValueError, "A and C must have the same number of columns." 102 if MD != MC: --> 103 raise ValueError, "C and D must have the same number of rows." 104 if ND != NB: 105 raise ValueError, "B and D must have the same number of columns." <type 'exceptions.ValueError'>: C and D must have the same number of rows. WARNING: Failure executing file: <testlti.py> Option 2 (with C as two rows...if C is a single row I do not get this traceback) /usr/lib/python2.5/site-packages/scipy/signal/ltisys.py in ss2tf(A, B, C, D, input) 147 148 num_states = A.shape[0] --> 149 type_test = A[:,0] + B[:,0] + C[0,:] + D 150 num = numpy.zeros((nout, num_states+1), type_test.dtype) 151 for k in range(nout): <type 'exceptions.ValueError'>: shape mismatch: objects cannot be broadcast to a single shape WARNING: Failure executing file: <testlti.py> Option 3 same as 1

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weave problems, weave_imp.o no such file or directory
by Søren Nielsen 02 Dec '08

02 Dec '08

Hi, I've done a fresh install of MinGw 5.14, Python 2.4.4, Scipy 0.6.0, Numpy 1.1.0 and numarray 1.5.2 When I try to use weave i get this: C:\>test_weave.py <weave: compiling> running build_ext running build_src building extension "sc_552cccf5dbf4f6eadd273cdcbd5860523" sources customize Mingw32CCompiler customize Mingw32CCompiler using build_ext customize Mingw32CCompiler customize Mingw32CCompiler using build_ext building 'sc_552cccf5dbf4f6eadd273cdcbd5860523' extension compiling C++ sources C compiler: g++ -mno-cygwin -O2 -Wall compile options: '-IC:\Python24\lib\site-packages\scipy\weave -IC:\Python24\lib\ site-packages\scipy\weave\scxx -IC:\Python24\lib\site-packages\numpy\core\includ e -IC:\Python24\include -IC:\Python24\PC -c' g++ -mno-cygwin -O2 -Wall -IC:\Python24\lib\site-packages\scipy\weave -IC:\Pytho n24\lib\site-packages\scipy\weave\scxx -IC:\Python24\lib\site-packages\numpy\cor e\include -IC:\Python24\include -IC:\Python24\PC -c C:\Python24\lib\site-package s\scipy\weave\scxx\weave_imp.cpp -o c:\docume~1\lisear~1\lokale~1\temp\Lise Arle th\python24_intermediate\compiler_08edc7e348e1c33f63a33ab500aef08e\Release\pytho n24\lib\site-packages\scipy\weave\scxx\weave_imp.o Found executable C:\MinGw\bin\g++.exe g++.exe: Arleth\python24_intermediate\compiler_08edc7e348e1c33f63a33ab500aef08e\ Release\python24\lib\site-packages\scipy\weave\scxx\weave_imp.o: No such file or directory Traceback (most recent call last): File "C:\test_weave.py", line 341, in ? main() File "C:\test_weave.py", line 224, in main weave.inline('printf("%d\\n",a);',['a'], verbose=2, type_converters=converte rs.blitz) #, compiler = 'msvc', verbpse=2, type_converters=converters.blitz, au to_downcast=0) #'msvc' or 'gcc' or 'mingw32' File "C:\Python24\Lib\site-packages\scipy\weave\inline_tools.py", line 338, in inline auto_downcast = auto_downcast, File "C:\Python24\Lib\site-packages\scipy\weave\inline_tools.py", line 447, in compile_function verbose=verbose, **kw) File "C:\Python24\Lib\site-packages\scipy\weave\ext_tools.py", line 365, in co mpile verbose = verbose, **kw) File "C:\Python24\Lib\site-packages\scipy\weave\build_tools.py", line 269, in build_extension setup(name = module_name, ext_modules = [ext],verbose=verb) File "C:\Python24\Lib\site-packages\numpy\distutils\core.py", line 184, in set up return old_setup(**new_attr) File "C:\Python24\lib\distutils\core.py", line 166, in setup raise SystemExit, "error: " + str(msg) distutils.errors.CompileError: error: Command "g++ -mno-cygwin -O2 -Wall -IC:\Py thon24\lib\site-packages\scipy\weave -IC:\Python24\lib\site-packages\scipy\weave \scxx -IC:\Python24\lib\site-packages\numpy\core\include -IC:\Python24\include - IC:\Python24\PC -c C:\Python24\lib\site-packages\scipy\weave\scxx\weave_imp.cpp -o c:\docume~1\lisear~1\lokale~1\temp\Lise Arleth\python24_intermediate\compiler _08edc7e348e1c33f63a33ab500aef08e\Release\python24\lib\site-packages\scipy\weave \scxx\weave_imp.o" failed with exit status 1 the test_weave file was something i found on the scipy dev wiki... I also tried some of my older files that also uses weave and they all give the same error... Can anyone help me with this?

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Create a spectrogram from a waveform
by Ed McCaffrey 01 Sep '08

01 Sep '08

Hello, I wrote a program in C# that creates a spectrogram from the waveform of a .wav music file. I now want to port it to Python, and I want to try to use SciPy instead of a direct port of the existing code, because I am not sure that it is perfectly accurate, and it is probably slow. I am having a hard time finding out how to do this with SciPy. With my code, I had a FFT function that took an array of real and imaginary components for each sample, and a second function taking both that produced the amplitude. The FFT function in SciPy just takes one array. Has anyone done this task in SciPy? Thanks.

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[ Python(x,y) ] New release : 2.0.4
by Pierre Raybaut 30 Aug '08

30 Aug '08

Hi all, As you may already know, Python(x,y) is a free scientific-oriented Python Distribution based on Qt and Eclipse providing a self-consistent scientific development environment. Release 2.0.4 is now available on http://www.pythonxy.com. (Full Edition, Basic Edition, and Update) The new Light Edition (i.e. Basic Edition without Eclipse: ~65MB) will be soon available on http://code.google.com/p/pythonxy Changes history Version 2.0.4 (08-30-2008) * Added: o PyQwt 5.1.0 - 2D plotting library (set of Python bindings for the Qwt library featuring fast plotting) o biopython 1.47 - Tools for computational molecular biology * Updated: o Pyrex 0.9.8.5 (Some minor bug fixes and improvements) o xy 1.0.4 (Minor bug fixes) Regards, Pierre Raybaut

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scikits.timeseries problem (error with e.g. cumprod)
by Martin Enlund 30 Aug '08

30 Aug '08

I am using scikits.timeseries and I found the toolkit very useful so far. However, I've run into a problem with functions such as cumprod, which just doesn't work (and I've thus created replacement functions using numpy functions) Even so, I'd like it to be solved seeing as I don't really like my ugly hacks. The error I get when trying to call cumprod is "TypeError: __call__() got an unexpected keyword argument 'dtype'" To replicate this error, try the following: ##### import numpy import scipy import scikits.timeseries as ts data = numpy.random.uniform(-1,1,90) new_series = ts.time_series(data, start_date=ts.now('D')-90) cp_series = new_series.cumprod() Btw, I am running this version of scikits.timeseries: '0.67.0.dev-r1228'

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Re: [SciPy-user] possible to get INF in divide by zero ?
by Vincent Favre-Nicolin 29 Aug '08

29 Aug '08

On jeudi 28 août 2008, Stef Mientki wrote: > I wonder if it's possible to get the MatLab behavior : > divide by zero gives infinite (INF) ? > > I even wonder if something like INF exists in python / scipy / numpy. Isn't this already the behaviour of numpy ? In [6]: ones(10)/0 Warning: divide by zero encountered in divide Out[6]: array([ Inf, Inf, Inf, Inf, Inf, Inf, Inf, Inf, Inf, Inf]) Vincent -- Vincent Favre-Nicolin CEA Grenoble/INAC/SP2M http://inac.cea.fr Univ. Joseph Fourier (Grenoble) http://www.ujf-grenoble.fr ObjCryst & Fox http://objcryst.sf.net/Fox

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