Mailman 3 November 2007 - NumPy-Discussion

is numpy.typeNA out of date?
by Darren Dale 26 Nov '07

26 Nov '07

Is the numpy.typeNA dictionary out of date? All of the verbose names for datatypes are captialized, and can't be found in the numpy namespace. Thanks, Darren

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"moving window" in numpy
by Matthew Perry 26 Nov '07

26 Nov '07

Hi all, I'm not sure if my terminology is familiar but I'm trying to do a "moving window" analysis (ie a spatial filter or kernel) on a 2-D array representing elevation. For example, a 3x3 window centered on each cell is used to calculate the derivate slope of that cell. Can this easily be implemented using numpy? Currently I have tried implementing in pure python loops (too slow) and c++ (fast but more difficult to compile, distribute, wrap in python calls, etc). I think a good solution would be to leverage numpy which is both fast and and easy package for end users to install. An example of the C++ code I'm trying to emulate is at http://perrygeo.net/download/hillshade.html . Does anyone have any tips or examples out there? Where should I start researching this? -- Matthew T. Perry http://www.perrygeo.net

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my derived ndarray class object loses its attribute after a transpose()
by Sebastian Haase 24 Nov '07

24 Nov '07

Hi, this question might habe been answered before: I have my own ndarray-derived class. I did this, so that I can add another "custom attribute" -- let's say arr.filename All works very except, except when I do arr2 = arr.transpose() my arr2 is still of the *type* of my derived class, however trying a arr2.filename now gives me an AtttributeError. What am I doing wrong? How can this be fixed? (I'm using numpy 1.0.1 - please let me know if this has been fixed since) Thanks, Sebastian Haase

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Installation of Python/mpl/numpy/scipy/Ipython for students
by mark 24 Nov '07

24 Nov '07

A question was posted a week or so ago on the scipy list about installing Python/mpl/numpy/scipy/Ipython by David Arnold (both Windows and Mac). He was interested in a simple install for students (and others that are less computer-savy). We had a little off-list correspondence, but thought to bring it back to the list, also posting on mpl (cause I read that list and it seems pretty responsive) and the numpy Google discussion group (they respond VERY quickly). On the scipy list it was suggested to use Sage reply, but that sounds like a little overkill to me. I have used the enthought package on windows successfully in class in the past, but I understand that they have now switched to eggs, which is not convenient (yet). I also don't like all the other things I have to set myself. A switch on the IDLE GUI to get mpl to work interactively (which is now seems impossible to do), and setting my PYTHONPATH with environment variables. It is all easy to do, but not for students, especially students without much knowledge of how computers work let alone access to set these variables and options. At one point I was reading about making a superpack (or a name like that) installation for Python with our favorite packages as mentioned above. I am not sure where that is going. Are others dreaming about such a superpack? What needs to be done to get it going? Mark

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loadtxt bug?
by Alan G Isaac 23 Nov '07

23 Nov '07

In numpy.core.numeric.py you will find loadtxt, which uses the following:: line = line[:line.find(comments)].strip() I believe there is a bug here (when a line has no comment). To illustrate:: >>> line = "12345" >>> comments = "#" >>> line[:line.find(comments)] '1234' So I propose this should be:: try: line = line[:line.index(comments)].strip() except ValueError: line = line.strip() Am I right? Cheers, Alan Isaac

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Re: [Numpy-discussion] OT: A Way to Approximate and Compress a 3D Surface
by Bob Lewis 23 Nov '07

23 Nov '07

On 11/20/07, Anne Archibald posted: > Subject: > Re: [Numpy-discussion] OT: A Way to Approximate and Compress a 3D Surface > From: > "Anne Archibald" <peridot.faceted(a)gmail.com> > Date: > Tue, 20 Nov 2007 17:13:31 -0500 > To: > "Discussion of Numerical Python" <numpy-discussion(a)scipy.org> > > To: > "Discussion of Numerical Python" <numpy-discussion(a)scipy.org> > > > On 20/11/2007, Geoffrey Zhu <zyzhu2000(a)gmail.com> wrote: > >> I have N tabulated data points { (x_i, y_i, z_i) } that describes a 3D >> surface. The surface is pretty "smooth." However, the number of data >> points is too large to be stored and manipulated efficiently. To make >> it easier to deal with, I am looking for an easy method to compress >> and approximate the data. Maybe the approximation can be described by >> far fewer number of coefficients. >> >> If you can give me some hints about possible numpy or non-numpy >> solutions or let me know where is better to ask this kind of question, >> I would really appreciate it. > > This is an important task in computer graphics, in particular, in the > field of multiresolution modelling. If you look up "surface > simplification" you'll find many references to articles. I don't know > of a library offhand that does it, let alone one that is accessible > from python, but you could try looking at a toolkit that does > isosurface visualization - these are surfaces that can often be > simplified enormously. In particular it looks like VTK might be able > to do what you want. Anne Archibald is correct that surface simplification may ultimately be of great help. Other place to look besides VTK are GTS, the GNU Triangulated Surface library, and CGAL, the Computational Geometry Algorithms Library, which has a Python binding. It occurs to me, though, that we should first verify that you do indeed have a surface in the first place. All you tell us is that you have a set of N points in 3-space. Are they connected? That is, does each point have well-defined neighbors? If so, do these vertices and connections form a mesh that defines a surface? - Bob Lewis

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Patch for numpy.i (not C89 compliant)
by Matthieu Brucher 23 Nov '07

23 Nov '07

Hi, I submitted a ticket and then a patch for numpy.i (http://projects.scipy.org/scipy/numpy/ticket/620). the problem is that some typemaps use a C99 syntax whereas most C compiler still are only C89 compliant (mainly Visual Studio). Matthieu -- French PhD student Website : http://miles.developpez.com/ Blogs : http://matt.eifelle.com and http://blog.developpez.com/?blog=92 LinkedIn : http://www.linkedin.com/in/matthieubrucher

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freebsd patch
by Stefan van der Walt 23 Nov '07

23 Nov '07

Hi all, Ticket 618 [1] proposes a patch to make numpy pass all tests on FreeBSD. Would anyone familiar with FreeBSD please glance over the patch, apply it and make sure that it works as intended? Thanks Stéfan [1] http://scipy.org/scipy/numpy/ticket/618

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numpy : your experiences?
by Rahul Garg 23 Nov '07

23 Nov '07

Hi. I have been a numpy user myself for some time now (though its my first message on this list). I am trying to do a informal survey for a univ related project .. I am a grad student btw working in comp sci. It would be awesome if you guys could respond to some of the following questions : a) Can you guys tell me briefly about the kind of problems you are tackling with numpy and scipy? b) Have you ever felt that numpy/scipy was slow and had to switch to C/C++/Fortran? c) Do you use any form of parallel processing? Multicores? SMPs? Clusters? If yes how did u utilize them? If you feel its not relevant to the list .. feel free to email me personally. I would be very interested in talking about these issues. thanks, rahul

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Adding ACML support
by Matthieu Brucher 23 Nov '07

23 Nov '07

Hi, I'm trying to get numpy work with AMD's MKL. The problem is that they not give a CBLAS interface, only the BLAS one. Can the numpy distutils check the existence of the cblas interface somewhere ? For the moment, it checks something with BLAS (but no actual testing takes place), but not CBLAS. Matthieu -- French PhD student Website : http://miles.developpez.com/ Blogs : http://matt.eifelle.com and http://blog.developpez.com/?blog=92 LinkedIn : http://www.linkedin.com/in/matthieubrucher

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