# [Matrix-SIG] inverse fft2d (complex case)

**Paul F. Dubois
**
Paul F. Dubois" <dubois1@llnl.gov

*Fri, 13 Nov 1998 19:59:08 -0800*

Frank,
I have added your new function to fft.py. It will appear in the next LLNL
release. Thanks for sending it in.
If you have time, please improve the test routine at the bottom of fft.py so
that it indicates whether or not the answers are correct, as I don't
remember enough about FFTs to do this without some research. I added a test
to see if your inverse inversed fft2d, which it did, but that is all I knew
how to do.
I'm sure any other functions you add to fft.py will be appreciated.
Thanks,
Paul
-----Original Message-----
From: Frank Horowitz <frank@ned.dem.csiro.au>
To: matrix-sig@python.org <matrix-sig@python.org>
Date: Friday, November 13, 1998 7:23 PM
Subject: [Matrix-SIG] inverse fft2d (complex case)
>*G'Day folks,
*>*
*>* I've been using NumPy (and Python) for a bit over a week now. To all
*>*who've contributed, I'd like to say "Great Job"! It's truly a pleasure
*>*to use...
*>*
*>* Even though it may be too trivial to warrant comment, I've implemented
*>*something that I felt the acute lack of in the LLNL NumPy distribution:
*>*the inverse of a 2d FFT (at least for the complex valued case; I hope
*>*to follow up with the equivalent real-valued inverse, once I grok the
*>*way that the wavenumbers are packed upon output from the forward
*>*2dfft). Without further ado, here is the code (all 2 lines of it :-)
*>*
*>*def inverse_fft2d(a, s=None, axes=(-2,-1)):
*>* return _raw_fft2d(a,s,axes,inverse_fft)
*>*
*>* I suppose it's debatable whether such a trivial extension belongs in
*>*the distribution. Indeed it's absence suggests some deeper issues (that
*>*I'm missing) have already been debated, and somebody decided that the
*>*implementation of an inverse properly belongs with the individual
*>*users. If so, pardon me for the intrusion :-)
*>*
*>* Obviously, I've also implemented ways of determining the appropriate
*>*wavenumbers, and will be happy to post them if anyone is interested.
*>*
*>* Cheers,
*>* Frank Horowitz
*>*
*>*_______________________________________________
*>*Matrix-SIG maillist - Matrix-SIG@python.org
*>*http://www.python.org/mailman/listinfo/matrix-sig
*>*
*>*
*