numpy.fft.ihfft
-
fft.ihfft(a, n=None, axis=-1, norm=None)
[source] -
Compute the inverse FFT of a signal that has Hermitian symmetry.
- Parameters
-
-
aarray_like
-
Input array.
-
nint, optional
-
Length of the inverse FFT, the number of points along transformation axis in the input to use. If
n
is smaller than the length of the input, the input is cropped. If it is larger, the input is padded with zeros. Ifn
is not given, the length of the input along the axis specified byaxis
is used. -
axisint, optional
-
Axis over which to compute the inverse FFT. If not given, the last axis is used.
-
norm{“backward”, “ortho”, “forward”}, optional
-
New in version 1.10.0.
Normalization mode (see
numpy.fft
). Default is “backward”. Indicates which direction of the forward/backward pair of transforms is scaled and with what normalization factor.New in version 1.20.0: The “backward”, “forward” values were added.
-
- Returns
-
-
outcomplex ndarray
-
The truncated or zero-padded input, transformed along the axis indicated by
axis
, or the last one ifaxis
is not specified. The length of the transformed axis isn//2 + 1
.
-
See also
-
hfft,
irfft
Notes
hfft
/ihfft
are a pair analogous torfft
/irfft
, but for the opposite case: here the signal has Hermitian symmetry in the time domain and is real in the frequency domain. So here it’shfft
for which you must supply the length of the result if it is to be odd:- even:
ihfft(hfft(a, 2*len(a) - 2)) == a
, within roundoff error, - odd:
ihfft(hfft(a, 2*len(a) - 1)) == a
, within roundoff error.
Examples
>>> spectrum = np.array([ 15, -4, 0, -1, 0, -4]) >>> np.fft.ifft(spectrum) array([1.+0.j, 2.+0.j, 3.+0.j, 4.+0.j, 3.+0.j, 2.+0.j]) # may vary >>> np.fft.ihfft(spectrum) array([ 1.-0.j, 2.-0.j, 3.-0.j, 4.-0.j]) # may vary
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https://numpy.org/doc/1.20/reference/generated/numpy.fft.ihfft.html