Mailman 3 April 2005 - SciPy-Dev

Fuzzy logic library for SciPy
by Prasan Samtani 16 May '05

16 May '05

Greetings scipy-devers, I am currently beginning work on a Fuzzy Logic toolkit in Python (modeled after the MatLab fuzzy logic toolbox http://www.mathworks.com/products/fuzzylogic/). Before I get ahead of myself, I was wondering if someone has already been working on something like this, I want to make sure I'm not reinventing the wheel. Thanks, Prasan

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EuroPython conference 2005
by Tiziano Zito 27 Apr '05

27 Apr '05

Is someone of the SciPy developers coming to the EuroPython conference this year? I think that Numeric3 and SciPy deserve a talk in the Science track. The announce on python-announce list follows: EuroPython is held -for the second time- in Göteborg, Sweden, during the week of June 27-29, 2005. Registration is open and now is your chance to submit a proposal (or more). Several topics are handled in parallel tracks at EuroPython2005, these include: Business, Education, Lightning talks, Python Frameworks, Python Language, Refereed papers, Science, Social skills/General topics, Tutorials/Neopythes, Zope and Zope Related, Zope Lightning talks. If you would like to tell the community something about your work, interest or experience, then then submit button is your way to go. The Refereed Track is intended for prestigious peer-reviewed talks for presenting technical and scientific papers. To our knowledge, EuroPython is the only Python conference, with peer-reviewed talks. Everybody can submit a paper for the Refereed Track, as long as it follows the Refereed paper instructions. For detailed information concerning this subject, please have a look at the Tracks & Talks webpage of EuroPython. To give you yet another opportunity to submit a refereed paper, we have extended the deadline to coincide with the deadline for regular talks. Lat day for submission is 1 May 2005! If you don't want to participate as a speaker, you might be interested in hearing the talks. Registration for EuroPython2005 is now open. Several registration alternatives are possible. Pre-Registration will be available until 17th of June, but Early Bird registration will end on May the 15th. Everybody is welcome: from novice to advanced. Our keynote speakers will be Guido van Rossum and Steve Pemberton. You may not have heard of Steve, since his focus is in an area that is not directly connected to Python. However, we expect him to give you an interesting perspective on what is going on in the industry. Find out more at http://homepages.cwi.nl/~steven/. If you don't know who Guido van Rossum is, you really need to come to Europython to find out. Feel free to spread the word about EuroPython2005 to your friends, family, colleagues, ... For all conference details, go to: http://www.europython.org See you at Göteborg. EuroPython Team. About EuroPython: Europython is an annual conference for the Python and Zope communities. It circulates between different sites in Europe. Having started in Charleroi, Belgium, it is now in Göteborg, Sweden and will move to CERN in Swizerland next year. Europython is a community conference run by volunteers.

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Bug fix in optimize/lbfgsb.py
by Ed Schofield 26 Apr '05

26 Apr '05

Hi all, This patch fixes a bug in SciPy 0.3.2 when passing user-defined arguments to the LBFGSB minimization routine. File: optimize/lbfgsb.py 179c179 < f[0], g = func_and_grad(x, *args) --- > f[0], g = func_and_grad(x) This bug is outstanding from version 0.3 (see http://www.scipy.net/pipermail/scipy-user/2004-June/002935.html). Best wishes, Ed

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Control Systems Module, Issues
by Venkat Raghavan 24 Apr '05

24 Apr '05

Hi Is it okay to implement the functions, name-wise, as it is done in Matlab. For example, say the series function in Matlab is implemented as : series(first param, second param). Is it okay to use the same function names? I think it's okay, but as I have never done this before, I am not sure. Also, this has the added advantage of easy portability of code across from Matlab, and lesser learning curve (if any). I've got my books out, and hope to have some results soon. The whole control systems module seems 'very doable' right now :) Regards, Venkat

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Re: [SciPy-user] Vector mean calculation?
by Travis Oliphant 22 Apr '05

22 Apr '05

Lance Boyle wrote: > > On Apr 21, 2005, at 5:41 PM, Fernando.Perez(a)colorado.edu wrote: > >> Quoting Thomas Davidoff <davidoff(a)haas.berkeley.edu>: >> >>> I have a vector with min equal to 412. Why am I getting a negative >>> mean? >> >> >> Without more details, it's quite difficult to be sure. Most likely, >> because >> it's very long and of integer type (ints are 32 bit objects, so you are >> effectively doing mod 2^31 arithmetic with negative wraparound). >> > Why does Python allow modular arithmetic when the user doesn't request > modular arithmetic? To get speed, scipy must assume that if you are using an integer array then you actually are requesting modular arithmetic (to the size of the integers in question). The other option would be to silently and automatically upcast when you get too large. I don't think that is the right way to go. It would be a good idea, however, to allow the user to specify a larger type within which to accomplish a reduction. Look for this in scipy.base (the new Numeric). I'm thinking of something like add.reduce(a, Int32) or add.reduce(a, Float64) which gives a return type for the array. -Travis

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An addition to basic.py
by Nils Wagner 21 Apr '05

21 Apr '05

Hi all, it would be nice if the following function could be added to basic.py in /Lib/linalg from scipy import * def vec(a): """vec function of the matrix a is the vector formed by stacking the columns of a on top of one another Reference: Alan J. Laub, Matrix Analysis for Scientists & Engineers SIAM 2005 """ if not a.iscontiguous(): a = reshape(a, a.shape) return concatenate(transpose(a)) # # A short test # a = rand(3,3) b = rand(3,3) c = rand(3,3) d = dot(a,dot(b,c)) x1 = vec(d) x2 = dot(linalg.kron(transpose(c),a),vec(b)) print 'x1-x2 should be zero',linalg.norm(x1-x2) Nils

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Control Systems Module
by Venkat Raghavan V.C. 20 Apr '05

20 Apr '05

Hi all, I am new to scipy and python. I have some experience in programming in C, and compiling stuff. I do have good control systems knowledge, including the math! I would like to write a Control Systems module for scipy, similiar to the one in Matlab. I have done quite a bit of programming in Matlab, though I don't think that's going to help me out in this regard, except maybe regarding design. The problem is, how do I get started off? I have about 3 months of time during summer which I intend to have finished this off. I would be grateful if someone gives me a general overview on how to go about it. I have found this netlib library, http://www.netlib.org/ieeecss/cascade/ after minimal searching. I also know of the scipy api docs. I just wanted to build a roadmap before I get started off! Regards, Venkat

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job openings at Enthought
by eric jones 20 Apr '05

20 Apr '05

Hey group, We have a number of scientific/python related jobs open. If you have any interest, please see: http://www.enthought.com/careers.htm thanks, eric

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SciPy.org brief outages planned
by Joe Cooper 19 Apr '05

19 Apr '05

Hi all, I'm preparing to migrate SciPy.org to a new server, and so I will be taking the SciPy.org community website offline for a few minutes a couple of times over the next few days. Given the current state of the old system (Plone eats way more than her fair share of memory, leaving the box slow and easily confused at time), it's likely no one will notice these outages, but I thought I'd give everyone a heads up just in case it takes longer than I expect. Anyway, no other services should be adversely impacted at this time, though there will be an hour or two of downtime when the final switch occurs, as I'll need to shutdown everything to do the final rsync of mail, web, and CVS data. I do not have a firm schedule for when the big switch will occur, but it is likely to be this week. Thanks!

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Logical operations, Numeric.sum() and overflow
by Ed Schofield 19 Apr '05

19 Apr '05

Hi all, Importing 'scipy' changes the output of the following code: >>>import random >>>import Numeric, RandomArray >>>(m,n) = (1000,3) >>>x = RandomArray.random((m,n)) >>>y = x < 0.5 >>>assert sum(y) == Numeric.sum(y) from nothing to an AssertionError. This is random behaviour: the error occurs about 90% of the time with this value of m on my PC (NumPy 23.1, SciPy 0.3.2, Python 2.4.1, Linux 2.6.11) , but reducing m to 500 makes it occur only about 20% of the time. There appear to be two causes: (1) importing scipy changes the behaviour of "y = x < 0.5" to return an array of typecode 'b' rather than 'l'. (2) Numeric.sum() is prone to overflow errors, returning an array of type 'b' rather than increasing precision: >>> a = Numeric.array([[253,254,255],[1,1,1]],'b') >>> Numeric.sum(a) array([254, 255, 0],'b') Here's my two cents. On point (1), unit tests are needed to ensure a simple 'import scipy' can't change the behaviour of unrelated Numpy code. (How is this even possible?) Point (2) seems to indicate a design flaw with Numeric. How do Octave and Matlab deal with this? Whatever they do, it "just works", whereas Numeric feels "broken" in this respect; this overflow propagates through other operations (Numeric.average() in my case), and finding such bugs can take hours. Any suggestions / ideas? -- Ed

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