Mailman 3 June 2001 - NumPy-Discussion

Re: [Numpy-discussion] math range error with Masked Array
by Joe Van Andel June 8, 2001

June 8, 2001

"Paul F. Dubois" wrote: > > Is the array single or double precision? Does it have the spacesaver > attribute set? The array is single precision, with the spacesave attribute set. > > Is it possible the data had bad values in it that were something other than > the missing value? What was the missing value? Yes, I finally found that the array had some contained some 'Nan' variables, because of an error in my earlier calculation. So, at this point, MA works for me. Thanks for your help. -- Joe VanAndel National Center for Atmospheric Research http://www.atd.ucar.edu/~vanandel/ Internet: vanandel(a)ucar.edu

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3d interpolation
by Robert.Denham＠dnr.qld.gov.au June 7, 2001

June 7, 2001

I have a series of x,y,z irregular data points. I would like to create a 2-d array (surface) from this data, each cell in the array being an interpolated value based on the nearby z values. I was wondering if anyone had any experience or suggestions under python? The interpolation algorithm needn't be elaborate, kriging is definite overkill, I was thinking more along the lines of splines or even inverse distance weighting. Thanks Robert Denham Department of Natural Resources Queensland, Australia ************************************************************************ The information in this e-mail together with any attachments is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any form of review, disclosure, modification, distribution and/or publication of this e-mail message is prohibited. If you have received this message in error, you are asked to inform the sender as quickly as possible and delete this message and any copies of this message from your computer and/or your computer system network. ************************************************************************

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vtkStructuredPoints
by Karshi Hasanov June 7, 2001

June 7, 2001

Hi, I wanna build *.vtk structured data file from an array A[i,j,k] which has a vector attributes. What's the right( or best) way of doing it using python? I do have the VTK User's Guide Book, but it didn't tell me much. Thanks

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20.1.0b2
by Paul F. Dubois June 6, 2001

June 6, 2001

20.1.0b2 is now available in tar.gz, .exe, .zip formats.

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undefined symbols when importing lapack
by David H. Marimont June 6, 2001

June 6, 2001

I just compiled and installed Numeric 20.1.0b1 using lapack and blas libraries. When I tried to import lapack_lite (after importing Numeric), I got this error: Traceback (most recent call last): File "<stdiimoprimporn>", line 1, in ? ImportError: /usr/lib/liblapack.so.3: undefined symbol: e_wsfe I'm using Python 2.1 on RH 7.1. I've had this problem before and have even seen postings to this list about related problems. But the solutions posted were over my head, so I've never been able to use the python interface to the lapack and blas libraries, which I really need. Does anyone have any advice, preferably pitched to someone who has limited compilation skills (i.e. at the the "configure, make, make install" level)? Thanks. David Marimont

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math range error with Masked Array
by Joe Van Andel June 6, 2001

June 6, 2001

I'm trying to use the MA package for numeric computations. Unfortunately, attempting to construct a masked array sometimes fails: masked_values(values, missingValue,savespace=1) File "/usr/lib/python2.1/site-packages/MA/MA.py", line 1299, in masked_values m = Numeric.less_equal(abs(d-value), atol+rtol*abs(value)) OverflowError: math range error The odd thing is that the floating point calculations that produced the input Numeric array didn't cause a math range error, but MA's attempt to find the 'missing' values does cause a range error. When I switched to Python2.1, I had to find and fix several overflow problems that didn't cause exceptions under Python1.5. For example, I had to use a "protected" exponentation routine to avoid overflow errors: MIN_EXP = -745 MAX_EXP = 709 def ProtExp(a): """ Protected Exponentiation calculation. Avoid Overflow error on large negative or positive arguments """ min_a = choose(less(a, MIN_EXP), (a, MIN_EXP)) return exp(choose(greater(min_a, MAX_EXP), (min_a, MAX_EXP)) ) ------------------- I'm concerned that the math exception handling for Python2.1 under x86 Linux makes it hard to get my work done. Any ideas on how to fix this error in MA? (I already tried masked_values(values, missingValue, rtol=1e-2,atol=1.e-4, savespace=1), which didn't help.) -- Joe VanAndel National Center for Atmospheric Research http://www.atd.ucar.edu/~vanandel/ Internet: vanandel(a)ucar.edu

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segfault when pickling PyObject arrays
by Tavis Rudd June 5, 2001

June 5, 2001

Hi, I've been having difficultly pickling arrays with the type PyObject using Numeric. I haven't tried it with MA but I assume the same problem exists. This script works ===================================== from cPickle import dump, load from Numeric import array, PyObject def pickleIt(obj, fileName): fp = open(fileName, 'w') dump(obj, fp) fp.close def loadIt(fileName): fp = open(fileName, 'r') obj = load(fp) fp.close() return obj a = array(['abc', 'def', 'ghi'], PyObject) pickleIt(a, 'test.pickle') This script segfaults ==================================== # ... same imports and func defs as above b = loadIt() print b ==================================== I first noticed this when trying to pickle arrays constructed from lists of mx.DateTime objects. Numeric 19.1.0 Python 2.1 final Linux 2.2.18 Is this a reproduceable bug or something unique to my setup? Tavis

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Re: [Numpy-discussion] Rich Comparisons and the Docs
by Chris Barker June 1, 2001

June 1, 2001

"Paul F. Dubois" wrote: > The doc source is not available. I try to keep it up to date. If you would > tell me the section I overlooked I will fix it. That would be: Special Topics: Comparisons > As to logical and and or, they are not available for overload in the rich > comparisons schema. That's a Python decision. I figured as much. I just took a look at PEP 207: Rich Comparisons, and interestingly enough, the orignal version by David Asher addressed this issue (at least in terms of chaining comparisons, such as a > b >c). In the final PEP, I foound this: 5 In the current proposal, when A<B returns an array of elementwise comparisons, this outcome is considered non-Boolean, and its interpretation as Boolean by the shortcut operators raises an exception. David Ascher's proposal tries to deal with this; I don't think this is worth the additional complexity in the code generator. Instead of A<B<C, you can write (A<B)&(B<C). I'm curious about the statement "I don't think this is worth the additional complexity". It seems like being able to override the boolean operators would be VERY useful, and it seems odd how quickly this was glossed over. It is extremely common to combine a boolean operator with a a comparison. Is it time for a "rich boolean operators" PEP, or was this really rejected for good reason? By the way, it doesn't seem to raise an exception for me, but it does give a wrong (uninuitive anyway)answer: >>> a = array([1,2,3]) >>> b = array([3,2,1]) >>> c = array([3,3,3]) >>> a < b < c array([0, 1, 1]) Also, does (A<B)&(B<C) always work? Is this a reliable solution? What do the bitwise operators do with Numeric arrays? I guess the final question here is: Is it time for a "rich boolean operators" PEP, or was this really rejected for good reason? -- Christopher Barker, Ph.D. ChrisHBarker(a)home.net --- --- --- http://members.home.net/barkerlohmann ---@@ -----@@ -----@@ ------@@@ ------@@@ ------@@@ Oil Spill Modeling ------ @ ------ @ ------ @ Water Resources Engineering ------- --------- -------- Coastal and Fluvial Hydrodynamics -------------------------------------- ------------------------------------------------------------------------

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