Mailman 3 January 2008 - SciPy-User

Help required regding Eigenvectors
by Sudheer Phani March 14, 2022

March 14, 2022

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 Sept. 10, 2009

Sept. 10, 2009

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 July 7, 2009

July 7, 2009

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 May 15, 2009

May 15, 2009

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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Installing Scipy
by David Arnold April 11, 2008

April 11, 2008

All, Mac OS X 10.4.11 PPC. Installed python from this: http://www.python.org/ftp/python/2.5.1/python-2.5.1-macosx.dmg Installation finishes with "There were errors installing the software. Please try installing again." Installing again makes no difference, but Python appears to be running: scipy-0.6.0 $ python Python 2.5.1 (r251:54869, Apr 18 2007, 22:08:04) [GCC 4.0.1 (Apple Computer, Inc. build 5367)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> Downloaded scipy from: http://prdownloads.sourceforge.net/scipy/ scipy-0.6.0.tar.gz?download After unpacking and changing directories, simply did this: scipy-0.6.0 $ sudo python setup.py install Seem to finish OK. Lots of "Warnings.' But testing according to INSTALL.txt resulted in: scipy-0.6.0 $ python Python 2.5.1 (r251:54869, Apr 18 2007, 22:08:04) [GCC 4.0.1 (Apple Computer, Inc. build 5367)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import scipy Traceback (most recent call last): File "<stdin>", line 1, in <module> File "scipy/__init__.py", line 54, in <module> from __config__ import show as show_config ImportError: No module named __config__ Any ideas or advice? Thanks David.

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illegal instruction error in scipy.linalg.decomp.svd
by Lev Givon March 11, 2008

March 11, 2008

On a Pentium 4 Linux box running python 2.5.1, scipy 0.6.0, numpy 1.0.4, and lapack 3.0, I recently noticed that scipy.linalg.decomp.svd() fails (and causes python to crash) with an "illegal instruction" error. A bit of debugging revealed that the error occurs in the line lwork = calc_lwork.gesdd(gesdd.prefix,m,n,compute_uv)[1] in scipy/linalg/decomp.py. Interestingly, scipy 0.5.2.1 on the same box (with all of the other software packages unchanged) does not exhibit this problem. Moreover, when I install scipy 0.6.0 along with all of the other packages on a Linux machine containing a Pentium D CPU, I do not observe the problem either. Being that I am running Mandriva Linux, closed scipy bug 540 caught my eye. I'm not sure how it could be related to the above problem, though (and I also do not know what the lapack patch mentioned in the ticket could have been - even though I have been maintaining Mandriva's lapack lately :-). Thoughts? L.G.

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Control Systems Toolbox
by Jasper Stolte March 5, 2008

March 5, 2008

Hi guys, I'm new to the list, nice to meet you all. Anyway my question is: Is there already someone developing some sort of Control Systems Toolbox / Robust Control Toolbox equivalent for SciPy? I would love to see it added, and I am thinking of building something from scratch. Obviously that wouldn't make much sense if other people are already working on something similar. Regards, Jasper

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Integrating
by Tommy Grav Feb. 19, 2008

Feb. 19, 2008

I am trying to write some code that needs to integrate orbits of asteroids forward and backwards in time. Is there some python interface out there to a runga-kutta 5th order integrator or a Bulirsch-Stoer integrator? Cheers Tommy

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exp2 or 2**
by Tom Johnson Feb. 12, 2008

Feb. 12, 2008

Are there reasons to use scipy.special.exp2 over 2** when operating on arrays? If so, what are they? Using 2** seems to be faster...

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compare two csv files
by Fabian Braennstroem Feb. 6, 2008

Feb. 6, 2008

Hi, I would like to compare two csv file; actually two columns from two csv files. I would use something like: def read_test(): start = time.clock() reader = csv.reader( file('data.txt') ) data = [ map(float, row) for row in reader ] data = array(data, dtype = float) To get my data into an array. Does anyone have an idea, how to compare the two columns? Would be nice! Fabian

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