[Numpy-discussion] Bug or surprising undocumented behaviour in irfft

2007-08-29 Thread Anne Archibald
Hi, numpy's Fourier transforms have the handy feature of being able to upsample and downsample signals; for example the documentation cites irfft(rfft(A),16*len(A)) as a way to get a Fourier interpolation of A. However, there is a peculiarity with the way numpy handles the highest-frequency

Re: [Numpy-discussion] Bug or surprising undocumented behaviour in irfft

2007-08-29 Thread Charles R Harris
Anne, On 8/29/07, Anne Archibald [EMAIL PROTECTED] wrote: Hi, numpy's Fourier transforms have the handy feature of being able to upsample and downsample signals; for example the documentation cites irfft(rfft(A),16*len(A)) as a way to get a Fourier interpolation of A. However, there is a

Re: [Numpy-discussion] Bug or surprising undocumented behaviour in irfft

2007-08-29 Thread Charles R Harris
On 8/29/07, Charles R Harris [EMAIL PROTECTED] wrote: Anne, On 8/29/07, Anne Archibald [EMAIL PROTECTED] wrote: Hi, numpy's Fourier transforms have the handy feature of being able to upsample and downsample signals; for example the documentation cites irfft(rfft(A),16*len(A)) as a

Re: [Numpy-discussion] Bug or surprising undocumented behaviour in irfft

2007-08-29 Thread Anne Archibald
On 29/08/2007, Charles R Harris [EMAIL PROTECTED] wrote: What is going on is that the coefficient at the Nyquist frequency appears once in the unextended array, but twice when the array is extended with zeros because of the Hermitean symmetry. That should probably be fixed in the upsampling

Re: [Numpy-discussion] Bug or surprising undocumented behaviour in irfft

2007-08-29 Thread Anne Archibald
On 29/08/2007, Charles R Harris [EMAIL PROTECTED] wrote: Is this also appropriate for the other FFTs? (inverse real, complex, hermitian, what have you) I have written a quick hack (attached) that should do just that rescaling, but I don't know that it's a good idea, as implemented.

Re: [Numpy-discussion] Bug or surprising undocumented behaviour in irfft

2007-08-29 Thread Charles R Harris
On 8/29/07, Anne Archibald [EMAIL PROTECTED] wrote: On 29/08/2007, Charles R Harris [EMAIL PROTECTED] wrote: Is this also appropriate for the other FFTs? (inverse real, complex, hermitian, what have you) I have written a quick hack (attached) that should do just that rescaling, but I