[Numpy-discussion] real and imag functions should produce errors for object arrays

2010-09-21 Thread Michael Gilbert
Hi, The following example demonstrates a rather unexpected result: import numpy x = numpy.array( complex( 1.0 , 1.0 ) , numpy.object ) print x.real (1+1j) print x.imag 0 Shouldn't real and imag return an error in such a situation? Thanks, Mike

[Numpy-discussion] IEEE 754-2008 decimal floating point support

2010-09-08 Thread Michael Gilbert
Hi, Are there any plans to add support for decimal floating point arithmetic, as defined in the 2008 revision of the IEEE 754 standard [0], in numpy? Thanks for any info. Best wishes, Mike [0] http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4610935tag=1

Re: [Numpy-discussion] IEEE 754-2008 decimal floating point support

2010-09-08 Thread Michael Gilbert
On Wed, 8 Sep 2010 09:43:56 -0600, Charles R Harris wrote: On Wed, Sep 8, 2010 at 9:26 AM, Michael Gilbert michael.s.gilb...@gmail.com wrote: Hi, Are there any plans to add support for decimal floating point arithmetic, as defined in the 2008 revision of the IEEE 754 standard [0

Re: [Numpy-discussion] IEEE 754-2008 decimal floating point support

2010-09-08 Thread Michael Gilbert
On Wed, Sep 8, 2010 at 12:23 PM, Charles R Harris wrote: On Wed, Sep 8, 2010 at 9:46 AM, Michael Gilbert michael.s.gilb...@gmail.com wrote: On Wed, 8 Sep 2010 09:43:56 -0600, Charles R Harris wrote: On Wed, Sep 8, 2010 at 9:26 AM, Michael Gilbert michael.s.gilb...@gmail.com wrote

Re: [Numpy-discussion] IEEE 754-2008 decimal floating point support

2010-09-08 Thread Michael Gilbert
On Wed, 8 Sep 2010 15:04:17 -0500, Robert Kern wrote: On Wed, Sep 8, 2010 at 14:44, Michael Gilbert michael.s.gilb...@gmail.com wrote: On Wed, Sep 8, 2010 at 12:23 PM, Charles R Harris wrote: On Wed, Sep 8, 2010 at 9:46 AM, Michael Gilbert michael.s.gilb...@gmail.com wrote: On Wed

Re: [Numpy-discussion] IEEE 754-2008 decimal floating point support

2010-09-08 Thread Michael Gilbert
On Wed, 8 Sep 2010 22:20:30 +0200, Sandro Tosi wrote: On Wed, Sep 8, 2010 at 22:10, Michael Gilbert michael.s.gilb...@gmail.com wrote: Here is an example:   0.3/3.0 - 0.1   -1.3877787807814457e-17   mpmath.mpf( '0.3' )/mpmath.mpf( '3.0' ) - mpmath.mpf( '0.1' )   mpf

Re: [Numpy-discussion] IEEE 754-2008 decimal floating point support

2010-09-08 Thread Michael Gilbert
On Wed, 8 Sep 2010 15:44:02 -0400, Michael Gilbert wrote: On Wed, Sep 8, 2010 at 12:23 PM, Charles R Harris wrote: On Wed, Sep 8, 2010 at 9:46 AM, Michael Gilbert michael.s.gilb...@gmail.com wrote: On Wed, 8 Sep 2010 09:43:56 -0600, Charles R Harris wrote: On Wed, Sep 8, 2010 at 9

Re: [Numpy-discussion] IEEE 754-2008 decimal floating point support

2010-09-08 Thread Michael Gilbert
On Wed, Sep 8, 2010 at 5:35 PM, Michael Gilbert wrote: On Wed, 8 Sep 2010 15:44:02 -0400, Michael Gilbert wrote: On Wed, Sep 8, 2010 at 12:23 PM, Charles R Harris wrote: On Wed, Sep 8, 2010 at 9:46 AM, Michael Gilbert michael.s.gilb...@gmail.com wrote: On Wed, 8 Sep 2010 09:43:56

[Numpy-discussion] Unexpected float96 precision loss

2010-09-01 Thread Michael Gilbert
Hi, I've been using numpy's float96 class lately, and I've run into some strange precision errors. See example below: import numpy numpy.version.version '1.5.0' sys.version '3.1.2 (release31-maint, Jul 8 2010, 01:16:48) \n[GCC 4.4.4]' x = numpy.array( [0.01] , numpy.float32 )

Re: [Numpy-discussion] Unexpected float96 precision loss

2010-09-01 Thread Michael Gilbert
On Wed, 1 Sep 2010 21:15:22 + (UTC), Pauli Virtanen wrote: Wed, 01 Sep 2010 16:26:59 -0400, Michael Gilbert wrote: I've been using numpy's float96 class lately, and I've run into some strange precision errors. [clip] x = numpy.array( [0.01] , numpy.float96 ) [clip] I would expect

Re: [Numpy-discussion] get information/position of value from matrix

2010-04-08 Thread Michael Gilbert
On Thu, 8 Apr 2010 09:06:16 +0200, ioannis syntychakis wrote: thanks for all your answers. Now i can get al the values above the 150, but i would also like to have their positions in de matrix. excample: [[1. 4. 5. 6. 7. 1 2. 5. 7. 8. 9. 3 3. 5. 7. 1. 3. 7]] so, if i now look for

Re: [Numpy-discussion] get information/position of value from matrix

2010-04-07 Thread Michael Gilbert
On Wed, 7 Apr 2010 16:40:24 +0200, ioannis syntychakis wrote: Hallo Everybody, I am new in this mail list and python. But I am working at something and I need your help. I have a very big matrix. What I want is to search in that matrix for values above the (for example:) 150. If there are

[Numpy-discussion] Possible improvement to numpy.mean()

2010-04-06 Thread Michael Gilbert
Hi, I am applying Monte Carlo for a problem involving mixed deterministic and random values. In order to avoid a lot of special handling and corner cases, I am using using numpy arrays full of a single value to represent the deterministic quantities. Anyway, I found that the standard deviation

[Numpy-discussion] warning or error for non-physical multivariate_normal covariance matrices?

2009-09-15 Thread Michael Gilbert
hi, when using numpy.random.multivariate_normal, would it make sense to warn the user that they have entered a non-physical covariance matrix? i was recently working on a problem and getting very strange results until i finally realized that i had actually entered a bogus covariance matrix. its

Re: [Numpy-discussion] warning or error for non-physical multivariate_normal covariance matrices?

2009-09-15 Thread Michael Gilbert
On Tue, 15 Sep 2009 13:26:23 -0500, Robert Kern wrote: On Tue, Sep 15, 2009 at 12:50, Charles R Harrischarlesr.har...@gmail.com wrote: On Tue, Sep 15, 2009 at 11:38 AM, Michael Gilbert michael.s.gilb...@gmail.com wrote: hi, when using numpy.random.multivariate_normal, would

Re: [Numpy-discussion] warning or error for non-physical multivariate_normal covariance matrices?

2009-09-15 Thread Michael Gilbert
On Tue, 15 Sep 2009 13:17:43 -0600, Charles R Harris wrote: On Tue, Sep 15, 2009 at 12:57 PM, Michael Gilbert michael.s.gilb...@gmail.com wrote: On Tue, 15 Sep 2009 13:26:23 -0500, Robert Kern wrote: On Tue, Sep 15, 2009 at 12:50, Charles R Harrischarlesr.har...@gmail.com wrote

Re: [Numpy-discussion] warning or error for non-physical multivariate_normal covariance matrices?

2009-09-15 Thread Michael Gilbert
On Tue, 15 Sep 2009 13:31:21 -0600, Charles R Harris wrote: On Tue, Sep 15, 2009 at 1:28 PM, Michael Gilbert michael.s.gilb...@gmail.com wrote: On Tue, 15 Sep 2009 13:17:43 -0600, Charles R Harris wrote: On Tue, Sep 15, 2009 at 12:57 PM, Michael Gilbert michael.s.gilb...@gmail.com

Re: [Numpy-discussion] Normalization of ifft

2009-03-26 Thread Michael Gilbert
On Thu, 26 Mar 2009 16:56:13 -0700 Lutz Maibaum wrote: Hello, I just started to use python and numpy for some numerical analysis. I have a question about the definition of the inverse Fourier transform. The user gives the formula (p.180) x[m] = Sum_k X[k] exp(j 2pi k m / n) where

Re: [Numpy-discussion] Another question on reading from binary FORTRAN file

2009-03-09 Thread Michael Gilbert
On Mon, 9 Mar 2009 18:21:45 -0400 Michael S. Gilbert wrote: On Mon, 9 Mar 2009 21:45:42 +0100, Mark Bakker wrote: Hello - I tried to figure this out from the list, but haven't succeeded yet. I have a simple FORTRAN binary file. It contains: 1 integer 1 float 1 array with 16

Re: [Numpy-discussion] loadtxt slow

2009-03-01 Thread Michael Gilbert
On Sun, 1 Mar 2009 16:12:14 -0500 Gideon Simpson wrote: So I have some data sets of about 16 floating point numbers stored in text files. I find that loadtxt is rather slow. Is this to be expected? Would it be faster if it were loading binary data? i have run into this as well.

Re: [Numpy-discussion] loadtxt slow

2009-03-01 Thread Michael Gilbert
On Sun, 1 Mar 2009 14:29:54 -0500 Michael Gilbert wrote: i have rewritten loadtxt to be smarter about allocating memory, but it is slower overall and doesn't support all of the original arguments/options (yet). i had meant to say that my version is slower for smaller data sets (when you

[Numpy-discussion] Mersenne twister seeds

2008-12-15 Thread Michael Gilbert
According to wikipedia [1], some common Mersenne twister algorithms use a linear congruential gradient (LCG) to generate seeds. LCGs have been known to produce poor random numbers. Does numpy's Mersenne twister do this? And if so, is this potentially a problem?

Re: [Numpy-discussion] On the quality of the numpy.random.normal() distribution

2008-12-11 Thread Michael Gilbert
Bruce Carneal did some tests of robustness and speed for various normal generators. I don't know what his final tests showed for Box-Muller. IIRC, it had some failures but nothing spectacular. The tests were pretty stringent and based on using the erf to turn the normal distribution into a

Re: [Numpy-discussion] numpy.random and multiprocessing

2008-12-11 Thread Michael Gilbert
Exactly, change task_helper.py to import numpy as np def task(x): import os print Hi, I'm, os.getpid() return np.random.random(x) and note the output Hi, I'm 16197 Hi, I'm 16198 Hi, I'm 16199 Hi, I'm 16199 [ 0.58175647 0.16293922 0.30488182

[Numpy-discussion] On the quality of the numpy.random.normal() distribution

2008-12-10 Thread Michael Gilbert
Hello, I have been reading that there may be potential issues with the Box-Muller transform, which is used by the numpy.random.normal() function. Supposedly, since f*x1 and f*x2 are not independent variables, then the individual elements (corresponding to f*x1 and f*x2 ) of the distribution