8000 ENH: add optional argument `dtype` to numpy.fft.fftfreq (#9126) by cval26 · Pull Request #16496 · numpy/numpy · GitHub
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ENH: add optional argument dtype to numpy.fft.fftfreq (#9126) #16496

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ENH: add optional argument dtype to numpy.fft.fftfreq (#9126) #16496

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77ec44d
ENH: add optional argument `dtype` to numpy.fft.fftfreq (#9126)
Jun 4, 2020
63ce40a
ENH: add optional argument `dtype` to numpy.fft.fftfreq (#9126)
Jun 4, 2020
3e8c289
Merge branch 'fftfreq-dtype' of github.com:cvav-git/numpy into fftfre…
Jun 13, 2020
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29 changes: 22 additions & 7 deletions numpy/fft/helper.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,8 @@

"""
from numpy.compat import integer_types
from numpy.core import integer, empty, arange, asarray, roll
from numpy.core import (integer, empty, arange, asarray, roll, reciprocal,
float32, float64)
from numpy.core.overrides import array_function_dispatch, set_module

# Created by Pearu Peterson, September 2002
Expand Down Expand Up @@ -122,7 +123,7 @@ def ifftshift(x, axes=None):


@set_module('numpy.fft')
def fftfreq(n, d=1.0):
def fftfreq(n, d=1.0, dtype=float64):
"""
Return the Discrete Fourier Transform sample frequencies.

Expand All @@ -140,7 +141,10 @@ def fftfreq(n, d=1.0):
n : int
Window length.
d : scalar, optional
Sample spacing (inverse of the sampling rate). Defaults to 1.
Sample spacing (inverse of the sampling rate). Defaults to 1.0.
dtype : object, optional
Output data type; either float32 or float64
Defaults to float64.

Returns
-------
Expand All @@ -160,18 +164,22 @@ def fftfreq(n, d=1.0):
"""
if not isinstance(n, integer_types):
raise ValueError("n should be an integer")
val = 1.0 / (n * d)
if dtype != float32:
dtype = float64

val = reciprocal(n*d, dtype=dtype)
results = empty(n, int)
N = (n-1)//2 + 1
p1 = arange(0, N, dtype=int)
results[:N] = p1
p2 = arange(-(n//2), 0, dtype=int)
results[N:] = p2

return results FBC0 * val


@set_module('numpy.fft')
def rfftfreq(n, d=1.0):
def rfftfreq(n, d=1.0, dtype=float64):
"""
Return the Discrete Fourier Transform sample frequencies
(for usage with rfft, irfft).
Expand All @@ -193,7 +201,10 @@ def rfftfreq(n, d=1.0):
n : int
Window length.
d : scalar, optional
Sample spacing (inverse of the sampling rate). Defaults to 1.
Sample spacing (inverse of the sampling rate). Defaults to 1.0.
dtype : object, optional
Output data type; either float32 or float64
Defaults to float64.

Returns
-------
Expand All @@ -216,7 +227,11 @@ def rfftfreq(n, d=1.0):
"""
if not isinstance(n, integer_types):
raise ValueError("n should be an integer")
val = 1.0/(n*d)
if dtype != float32:
dtype = float64

val = reciprocal(n*d, dtype=dtype)
N = n//2 + 1
results = arange(0, N, dtype=int)
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Sorry one last thought. Would it make sense to cast this to dtype as well?

Suggested change
results = arange(0, N, dtype=int)
results = arange(0, N, dtype=dtype)

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@cval26 cval26 Jun 30, 2020 •
edited
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we could but from what I understand this is always just an array of integers, which when multiplied with the dtype cast val will lead to the returned result being of type dtype anyway, right?


return results * val
0