Mailman 3 September 2006 - 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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FAIL: check_dot (scipy.linalg.tests.test_blas.test_fblas1_simple)
by Andrew Jaffe 16 Nov '06

16 Nov '06

Hi All- I get the following error with scipy.__version__ = '0.5.0.2121' on PPC OSX 2.4.3 Universal Build with numpy 1.0.2889 (note that the latter has a known longdouble problem, but I don't think that's related). Indeed the fblas complex [c,z]dot[c,u] functions do seem to fail. (In fact, zdotc([1,-4,3],[2,3,1]) hangs the interpreter...) Andrew ====================================================================== FAIL: check_dot (scipy.linalg.tests.test_blas.test_fblas1_simple) ---------------------------------------------------------------------- Traceback (most recent call last): File "/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/site-packages/scipy-0.5.0.2121-py2.4-macosx-10.3-fat.egg/scipy/linalg/tests/test_blas.py", line 75, in check_dot assert_almost_equal(f([3j,-4,3-4j],[2,3,1]),-9+2j) File "/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/site-packages/numpy-1.0.2889-py2.4-macosx-10.3-fat.egg/numpy/testing/utils.py", line 156, in assert_almost_equal assert round(abs(desired - actual),decimal) == 0, msg AssertionError: Items are not equal: ACTUAL: (-1.9980511665344238+2.1130658899732593e-36j) DESIRED: (-9+2j) ====================================================================== FAIL: check_dot (scipy.lib.tests.test_blas.test_fblas1_simple) ---------------------------------------------------------------------- Traceback (most recent call last): File "/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/site-packages/scipy-0.5.0.2121-py2.4-macosx-10.3-fat.egg/scipy/lib/blas/tests/test_blas.py", line 76, in check_dot assert_almost_equal(f([3j,-4,3-4j],[2,3,1]),-9+2j) File "/Library/Frameworks/Python.framework/Versions/2.4/lib/python2.4/site-packages/numpy-1.0.2889-py2.4-macosx-10.3-fat.egg/numpy/testing/utils.py", line 156, in assert_almost_equal assert round(abs(desired - actual),decimal) == 0, msg AssertionError: Items are not equal: ACTUAL: (-1.9980511665344238+2.1996782422872647e-36j) DESIRED: (-9+2j)

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Is anybody working on a toolbox for Kalman filtering and derivative ?
by David Cournapeau 04 Oct '06

04 Oct '06

Hi, I wanted to know if anyone is developing, or know a toolbox for kalman filtering and derivative (particle filter, non linear kalman, etc...) ? I am working right now on (simple, linear, Gaussian) Kalman filtering, would like to extend it, and I thought it would be a great addition to scipy, and I would like to avoid duplicating works, David

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access to wavelets.scipy.org/svn/
by Glen W. Mabey 03 Oct '06

03 Oct '06

Hello, I don't know of a better place to post than this for a question regarding pywt. Following the instructions found at http://wavelets.scipy.org/index.html for checking out the development version: $$ svn co http://wavelets.scipy.org/svn/multiresolution/wavelets/trunk wavelets svn: REPORT request failed on '/svn/multiresolution/!svn/vcc/default' svn: REPORT of '/svn/multiresolution/!svn/vcc/default': 400 Bad Request (http://wavelets.scipy.org) and the indicated path in http://wavelets.scipy.org/svn/multiresolution/pywt/trunk/README.txt yields a similar error. However, trying: $$ svn co https://wavelets.scipy.org/svn/multiresolution/pywt/trunk/ at least asks for a password. However, shouldn't there be (or, could there please be) anonymous access to this tree? Thank you, Glen Mabey

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Pros and Cons of Python verses other array environments
by Travis Oliphant 02 Oct '06

02 Oct '06

Hi all, I've started a possibly controversial but hopefully informative page that tries to list some of the advantages of using Python+NumPy+Scipy+Matplotlib+IPython (I'm calling that combination PyLab) versus other array environments. The purpose is not to go into detail about semantic differences, but document higher-level differences that might help somebody decide whether or not they could use NumPy instead of some other environment. I've started with a comparison to MATLAB, based on an email response I sent to a friend earlier today. Additions and corrections welcome. -Travis O.

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error building pyopengl...
by fred 02 Oct '06

02 Oct '06

Hi the list, Yes, I know it's a little bit OT, but I saw on Wilna DuToit Scipy webpage his mat3d.py and thus I need to build PyOpenGL (2.0.2.01). I can't build it because gcc failed with exit status 1... What do I need to build it ? PyOpenGL seems to be quite old on sourceforge and not to be still maintained. Cheers, PS : python2.4, swig 1.3.23 -- « Python, c'est un peu comme la baïonnette en 14, faut toujours sortir avec, et pas hésiter d'en mettre un coup en cas de besoin. » J.-Ph. D.

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Q: Building SciPy for Windows without Cygwin dependency?
by Kyle Ferrio 01 Oct '06

01 Oct '06

I want to build a full-up SciPy for MS Windows in line with the Python and SciPy licenses. I noticed the following text in the excellent installation instructions, regarding the choice of compiler: "Cygwin is required if you want to build ATLAS yourself." Well, I often build ATLAS myself. And now (implicitly) I want to build ATLAS in a way that is available to SciPy. So I have two questions: 1. Must ATLAS -- to be used with SciPy -- be built with a dependence on the GPL'ed Cygwin runtime library? (I can't imagine why this would be the case, but I want to test my understanding.) 2. Is the "need" for Cygwin actually just a way to get (extremely convenient) tools like 'ar' which do not infect the ATLAS lib with the GPL? Thanks!

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Running mean: numpy or pyrex?
by David Finlayson 01 Oct '06

01 Oct '06

I need to run a series of convolution filters over swath bathymetry data. The data is spaced in track lines approximately 4048 samples across and several million lines long. Currently, I have the data in a python 2D list and then send several variations of a running mean down the track. I was fairly impressed with the filter performance using psyco until I met some truly huge files. Now I am wondering if I would get any speed benefit from using numpy (for the 2D array access) or would I be better off trying pyrex for the running mean loops? One of the issues I am facing is the possibility that very large files may need to be read from the disk as needed instead of holding the whole thing in ram. I also need to distrubute this code to my team, so minimizing the pain of installing numeric and other packages would be an issue. Should I expect significant speed benefits from a numy version of this type of code? Note that I have already made the simple optimization to calculate the full mean only the first iteration and just update the mean with the new data for the remaining iterations. Thanks for any advise you might have. -- David Finlayson

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Re: [SciPy-user] Pros and Cons of Python verses other array environments
by R. Padraic Springuel 01 Oct '06

01 Oct '06

For those of you objecting to the "difficulty" in importing several different packages to get all the different capabilities here going at once, there is an easy fix here suggested by Travis's use of Pylab as the title for the grouping. If you look at matplotlib's pylab.py file that it places in your site-packages directory, its just redirects the import statement to find what's needed. Add a few lines to this file and it can pull in numpy, scipy, and IPython at the same time. What might make things easier for the beginner would be to have all of the packages Travis mentioned available in a bundled download that is easily installable (like Enthought Python, but without the extra bells & whistles) and with a modified version of the pylab.py file that contains all the necessary import statements. It might also be nice if this kind of package would automatically configure the interpreter to issue the necessary import statements automatically when it starts. In this way, the beginner need not learn about import statements right away. All the basics are right there for them. -- R. Padraic Springuel Teaching Assistant Department of Physics and Astronomy University of Maine Bennett 309 Office Hours: Wednesday 2-3pm

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