Mailman 3 May 2002 - NumPy-Discussion

Bug: extremely misleading array behavior
by Larry Denneau June 3, 2002

June 3, 2002

Hello, I recently discovered the following behavior when fetching values from a Numeric array. Can somebody offer some insight? #1) import Numeric a = Numeric.zeros((2, 2), 'i') n = a[1, 1] # fetch interesting value from array print n a[1, 1] = 10 # change array print n # blam print type(n) # huh [bash]$ python 1.py 0 10 <type 'array'> but #2) import Numeric a = Numeric.zeros((2,), 'i') n = a[1] print n a[1] = 10 print n print type(n) [bash]$ python 2.py 0 0 <type 'int'> #2 works the way one would expect, and #1 does not (n changes). They should at least both behave the same. :-) At a minimum, naive use of arrays can lead to confusing or disastrous results, since a single value fetched from an array can change behind your back. It appears n is aliased into a, but preserves its value when a is deleted (with del(a)). What happens to the "rest of" a? I'm using Python 2.2, Numeric-21.0, on both Unix and Win32. Thanks, Larry

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Announcing PyQwt = FAST and EASY data plotting for Python, Numeric and Qt!
by Gerard Vermeulen May 30, 2002

May 30, 2002

Announcing PyQwt-sip324_041 PyQwt = FAST and EASY data plotting for Python, Numeric and Qt! PyQwt is a set of Python bindings for the Qwt C++ class library. The Qwt library extends the Qt framework with widgets for scientific and engineering applications. It contains QwtPlot, a 2d plotting widget, and widgets for data input/output such as and QwtCounter, QwtKnob, QwtThermo and QwtWheel. PyQwt requires and extends PyQt, a set of Python bindings for Qt. PyQwt requires Numeric. Numeric extends the Python language with new data types that make Python an ideal language for numerical computing and experimentation (maybe less efficient than MatLab, but more expressive). The home page of PyQwt is http://gerard.vermeulen.free.fr NEW and IMPORTANT FEATURES of PyQwt-sip324_041: 1. requires PyQt-3.2.4 and sip-3.2.4. 2. implements practically all public and protected member functions of Qwt-0.4.1. 3. compatible with Numeric-21.0 and lower. 4. simplified setup.py script for Unix/Linux and Windows. 5. *.exe installer for Windows (requires Qt-2.3.0-NC). 6. HTML documentation with installation instructions and a reference listing the Python calls to PyQwt that are different from the corresponding C++ calls to Qwt. 7. Tested on Linux with Qt-2.3.1 and Qt-3.0.4. Tested on Windows with Qt-2.3.0-NC. Gerard Vermeulen

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assignment to matrix slice in Numeric bug/feature?
by Roman Suzi May 25, 2002

May 25, 2002

hello, I've found that the following fragment of code gives an error while with other shapes of b there is no problem: ---------------------------- #!/usr/bin/python2 from Numeric import * from Matrix import * a = Matrix(zeros([4,4])) b = Matrix(ones([2,1])) print a, a.shape print b, b.shape q = a[1:3,1:2] print q, q.shape a[1:3,1:2] = b ----------------------------- resulting in: ------------------------------------- Matrix([[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]) (4, 4) Matrix([[1], [1]]) (2, 1) Matrix([[0], [0]]) (2, 1) Traceback (most recent call last): File "./numpybug.py", line 11, in ? a[1:3,1:2] = b File "/usr/lib/python2.1/site-packages/Numeric/Matrix.py", line 180, in __setitem__ def __setitem__(self, index, value): self.array[index] = asarray(squeeze(value),self._typecode) ValueError: matrices are not aligned for copy ----------------------------------------------- The mentioned behaviour looks like a bug, because a[1:3,1:2] and b have the same shape and according to docs b must be copied to a-slice 1:1... Numeric is version 21.0, Python 2.1 under Linux RedHat 7.2. Thank you in advance! Sincerely yours, Roman Suzi -- \_ Russia \_ Karelia \_ Petrozavodsk \_ rnd(a)onego.ru \_ \_ Saturday, May 18, 2002 \_ Powered by Linux RedHat 7.2 \_

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Bug in MLab.std()
by Jonathan M. Gilligan May 24, 2002

May 24, 2002

I submitted this to the Sourceforge bug tracker, but wanted also to let this list know, as this is a potentially nasty bug. MLab.std() gives completely incorrect answers for multidimensional arrays when axis != 0. >>> foo array([[[ 1., 1., 1.], [ 2., 2., 2.], [ 3., 3., 3.]], [[ 1., 4., 4.], [ 2., 5., 5.], [ 3., 6., 6.]]]) >>> std(foo) array([[ 0. , 2.12132034, 2.12132034], [ 0. , 2.12132034, 2.12132034], [ 0. , 2.12132034, 2.12132034]]) >>> std(foo, 1) array([[ 0., 0., 0.], [ 0., 0., 0.]]) The following should fix the problem (but I haven't tested it extensively): def std(m,axis=0): """std(m,axis=0) returns the standard deviation along the given dimension of m. The result is unbiased with division by N-1. If m is of integer type returns a floating point answer. """ x = asarray(m) n = float(x.shape[axis]) x2 = mean(x * x, axis) x = mean(x, axis) return sqrt((x2 - x * x) * n /(n-1.0)) Jonathan Gilligan

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Installation woes
by Eric Hagemann May 24, 2002

May 24, 2002

Hey All, Doing my first install on a linux system (Mandrake 8.2 on a PPC). I downloaded the *.tar.gz and unzip/untarred it. I enter the command 'python setup.py install' and get the following error "open '/usr/lib/python2.2/config/Makefile' (No such file or directory)" This is the python that comes with mandrake. I have been able to download and install a new version of python2.2 and sucessfully install Numpy there but I was wondering what I needed to do to get it running in the 'base' python install any pointers ? Cheers Eric

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RE: Numpy-discussion digest, Vol 1 #463 - 1 msg
by Tariq Rashid May 22, 2002

May 22, 2002

i'm interested in this too? in fact i am willing to help write some wavelet tools for python - but you'll have to be patient as i've only just started on my PyObjects et al ... and i'm not an expert either - just very interested and entheusiastic! Tariq Rashid -----Original Message----- From: numpy-discussion-admin(a)lists.sourceforge.net [mailto:numpy-discussion-admin@lists.sourceforge.net]On Behalf Of numpy-discussion-request(a)lists.sourceforge.net Sent: 22 May 2002 20:05 To: numpy-discussion(a)lists.sourceforge.net Subject: Numpy-discussion digest, Vol 1 #463 - 1 msg Send Numpy-discussion mailing list submissions to numpy-discussion(a)lists.sourceforge.net To subscribe or unsubscribe via the World Wide Web, visit https://lists.sourceforge.net/lists/listinfo/numpy-discussion or, via email, send a message with subject or body 'help' to numpy-discussion-request(a)lists.sourceforge.net You can reach the person managing the list at numpy-discussion-admin(a)lists.sourceforge.net When replying, please edit your Subject line so it is more specific than "Re: Contents of Numpy-discussion digest..." Today's Topics: 1. Q: Wavelet tools with Python (Zaur Shiboukhov) --__--__--

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Q: Wavelet tools with Python
by Zaur Shiboukhov May 22, 2002

May 22, 2002

How is about wavelet tools with Python? Zaur --__--__-- _______________________________________________ Numpy-discussion mailing list Numpy-discussion(a)lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/numpy-discussion End of Numpy-discussion Digest

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Q: Wavelet tools with Python
by Zaur Shiboukhov May 22, 2002

May 22, 2002

How is about wavelet tools with Python? Zaur --__--__-- _______________________________________________ Numpy-discussion mailing list Numpy-discussion(a)lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/numpy-discussion End of Numpy-discussion Digest

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Q: Wavelet tools with Python
by Zaur Shiboukhov May 22, 2002

May 22, 2002

How is about wavelet tools with Python? Zaur

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[ANN] Chaco: A 2D scientific graphics library
by eric May 17, 2002

May 17, 2002

I'm happy to announce that Enthought is developing a platform independent plotting library for Python. The Chaco project, as it is named, is funded by the Space Telescope Science Institute (STScI) and licensed under a BSD style open source license. Chaco is designed for presentation quality scientific 2D graphics on a variety of output devices. The initial targets are wxPython, TkInter, Mac OS X, and PDF for hard copy output. It's design is extensible so that other backends, such as OpenGL, can be added. Currently, the low-level API for wxPython, Mac OS X, and PDF are operational. The high level graphics objects will be developed over the coming months. Chaco is hosted at the SciPy site. For more information visit: http://www.scipy.org/site_content/chaco People are invited to comment on and contribute to the project. Chaco's discussion list is: scipy-chaco(a)scipy.org To subscribe, go to the mailing list's info page: http://scipy.net/mailman/listinfo/scipy-chaco thanks, eric jones -- Eric Jones <eric at enthought.com> Enthought, Inc. [www.enthought.com and www.scipy.org] (512) 536-1057

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