diff options
Diffstat (limited to 'numpy/fft/fftpack.py')
| -rw-r--r-- | numpy/fft/fftpack.py | 113 |
1 files changed, 58 insertions, 55 deletions
diff --git a/numpy/fft/fftpack.py b/numpy/fft/fftpack.py index 12c207cb0..0af1cdc79 100644 --- a/numpy/fft/fftpack.py +++ b/numpy/fft/fftpack.py @@ -109,23 +109,26 @@ def fft(a, n=None, axis=-1): def ifft(a, n=None, axis=-1): """ - Compute the one-dimensonal inverse fft on a given axis. + Compute the one-dimensonal inverse fft along an axis. - Return the n point inverse discrete Fourier transform of a. n - defaults to the length of a. If n is larger than the length of a, - then a will be zero-padded to make up the difference. If n is - smaller than the length of a, then a will be truncated to reduce - its size. + Return the `n` point inverse discrete Fourier transform of `a`. The length + `n` defaults to the length of `a`. If `n` is larger than the length of `a`, + then `a` will be zero-padded to make up the difference. If `n` is smaller + than the length of `a`, then `a` will be truncated to reduce its size. Parameters ---------- - a : array - input array - n : int - length of the fft - axis : int - axis over which to compute the inverse fft + a : array_like + Input array. + n : int, optional + Length of the fft. + axis : int, optional + Axis over which to compute the inverse fft. + + See Also + -------- + fft Notes ----- @@ -135,10 +138,10 @@ def ifft(a, n=None, axis=-1): This is the inverse of fft: ifft(fft(a)) == a within numerical accuracy. - This is most efficient for n a power of two. This also stores a cache of + This is most efficient for `n` a power of two. This also stores a cache of working memory for different sizes of fft's, so you could theoretically run into memory problems if you call this too many times with too many - different n's. + different `n` values. """ @@ -189,34 +192,35 @@ def irfft(a, n=None, axis=-1): """ Compute the one-dimensional inverse fft for real input. - Notes - ----- - - Return the real valued n point inverse discrete Fourier transform - of a, where a contains the nonnegative frequency terms of a - Hermite-symmetric sequence. n is the length of the result, not the - input. If n is not supplied, the default is 2*(len(a)-1). If you - want the length of the result to be odd, you have to say so. - Parameters ---------- - a : array - input array with real data type + Input array with real data type. n : int - length of the fft + Length of the fft. axis : int - axis over which to compute the fft + Axis over which to compute the fft. + + See Also + -------- + rfft Notes ----- + Return the real valued `n` point inverse discrete Fourier transform + of `a`, where `a` contains the nonnegative frequency terms of a + Hermite-symmetric sequence. `n` is the length of the result, not the + input. If `n` is not supplied, the default is 2*(len(`a`)-1). If you + want the length of the result to be odd, you have to say so. - If you specify an n such that a must be zero-padded or truncated, the + If you specify an `n` such that `a` must be zero-padded or truncated, the extra/removed values will be added/removed at high frequencies. One can thus resample a series to m points via Fourier interpolation by: a_resamp = irfft(rfft(a), m). - This is the inverse of rfft: irfft(rfft(a), len(a)) == a within numerical accuracy. + Within numerical accuracy ``irfft`` is the inverse of ``rfft``:: + + irfft(rfft(a), len(a)) == a """ @@ -240,6 +244,11 @@ def hfft(a, n=None, axis=-1): axis : int axis over which to compute the hfft + See also + -------- + rfft + ihfft + Notes ----- These are a pair analogous to rfft/irfft, but for the @@ -250,11 +259,6 @@ def hfft(a, n=None, axis=-1): ihfft(hfft(a), len(a)) == a within numerical accuracy. - See also - -------- - rfft - ihfft - """ a = asarray(a).astype(complex) @@ -265,17 +269,20 @@ def hfft(a, n=None, axis=-1): def ihfft(a, n=None, axis=-1): """ - Compute the inverse fft of a signal which spectrum has Hermitian - symmetry. + Compute the inverse fft of a signal whose spectrum has Hermitian symmetry. Parameters ---------- - a : array - input array - n : int - length of the ihfft - axis : int - axis over which to compute the ihfft + a : array_like + Input array. + n : int, optional + Length of the ihfft. + axis : int, optional + Axis over which to compute the ihfft. + + See also + -------- + rfft, hfft Notes ----- @@ -287,11 +294,6 @@ def ihfft(a, n=None, axis=-1): ihfft(hfft(a), len(a)) == a within numerical accuracy. - See also - -------- - rfft - hfft - """ a = asarray(a).astype(float) @@ -395,20 +397,21 @@ def ifftn(a, s=None, axes=None): def fft2(a, s=None, axes=(-2,-1)): """ - Compute the 2d fft of an array. + Compute the 2-D FFT of an array. Parameters ---------- - a : array - input array - s : sequence (int) - shape of the fft - axis : int - axis over which to compute the fft + a : array_like + Input array. The rank (dimensions) of `a` must be 2 or greater. + s : shape tuple + Shape of the FFT. + axes : sequence of 2 ints + The 2 axes over which to compute the FFT. The default is the last two + axes (-2, -1). Notes ----- - This is really just fftn with different default behavior. + This is really just ``fftn`` with different default behavior. """ |