[Numpy-discussion] Another reality check

David Goldsmith d.l.goldsmith@gmail....
Sun Jul 11 21:36:17 CDT 2010

```On Sun, Jul 11, 2010 at 6:18 PM, David Goldsmith <d.l.goldsmith@gmail.com>wrote:

> In numpy.fft we find the following:
>
> "Then A[1:n/2] contains the positive-frequency terms, and A[n/2+1:]contains the negative-frequency terms, in order of decreasingly negative
> frequency."
>
> Just want to confirm that "decreasingly negative frequency" means ...,
> A[n-2] = A_(-2), A[n-1] = A_(-1), as implied by our definition (attached).
>
> DG
>

And while I have your attention :-)

"For an odd number of input points, A[(n-1)/2] contains the largest positive
frequency, while A[(n+1)/2] contains the largest [in absolute value]
negative frequency."  Are these not also termed Nyquist frequencies?  If
not, would it be incorrect to characterize them as "the largest realizable
frequencies" (in the sense that the data contain no information about any
higher frequencies)?

DG
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