Module « scipy.fft »

Fonction rfftn - module scipy.fft

Signature de la fonction rfftn

def rfftn(x, s=None, axes=None, norm=None, overwrite_x=False, workers=None, *, plan=None) 

Description

rfftn.__doc__

    Compute the N-D discrete Fourier Transform for real input.

    This function computes the N-D discrete Fourier Transform over
    any number of axes in an M-D real array by means of the Fast
    Fourier Transform (FFT). By default, all axes are transformed, with the
    real transform performed over the last axis, while the remaining
    transforms are complex.

    Parameters
    ----------
    x : array_like
        Input array, taken to be real.
    s : sequence of ints, optional
        Shape (length along each transformed axis) to use from the input.
        (``s[0]`` refers to axis 0, ``s[1]`` to axis 1, etc.).
        The final element of `s` corresponds to `n` for ``rfft(x, n)``, while
        for the remaining axes, it corresponds to `n` for ``fft(x, n)``.
        Along any axis, if the given shape is smaller than that of the input,
        the input is cropped. If it is larger, the input is padded with zeros.
        if `s` is not given, the shape of the input along the axes specified
        by `axes` is used.
    axes : sequence of ints, optional
        Axes over which to compute the FFT. If not given, the last ``len(s)``
        axes are used, or all axes if `s` is also not specified.
    norm : {"backward", "ortho", "forward"}, optional
        Normalization mode (see `fft`). Default is "backward".
    overwrite_x : bool, optional
        If True, the contents of `x` can be destroyed; the default is False.
        See :func:`fft` for more details.
    workers : int, optional
        Maximum number of workers to use for parallel computation. If negative,
        the value wraps around from ``os.cpu_count()``.
        See :func:`~scipy.fft.fft` for more details.
    plan : object, optional
        This argument is reserved for passing in a precomputed plan provided
        by downstream FFT vendors. It is currently not used in SciPy.

        .. versionadded:: 1.5.0

    Returns
    -------
    out : complex ndarray
        The truncated or zero-padded input, transformed along the axes
        indicated by `axes`, or by a combination of `s` and `x`,
        as explained in the parameters section above.
        The length of the last axis transformed will be ``s[-1]//2+1``,
        while the remaining transformed axes will have lengths according to
        `s`, or unchanged from the input.

    Raises
    ------
    ValueError
        If `s` and `axes` have different length.
    IndexError
        If an element of `axes` is larger than than the number of axes of `x`.

    See Also
    --------
    irfftn : The inverse of `rfftn`, i.e., the inverse of the N-D FFT
         of real input.
    fft : The 1-D FFT, with definitions and conventions used.
    rfft : The 1-D FFT of real input.
    fftn : The N-D FFT.
    rfft2 : The 2-D FFT of real input.

    Notes
    -----
    The transform for real input is performed over the last transformation
    axis, as by `rfft`, then the transform over the remaining axes is
    performed as by `fftn`. The order of the output is as for `rfft` for the
    final transformation axis, and as for `fftn` for the remaining
    transformation axes.

    See `fft` for details, definitions and conventions used.

    Examples
    --------
    >>> import scipy.fft
    >>> x = np.ones((2, 2, 2))
    >>> scipy.fft.rfftn(x)
    array([[[8.+0.j,  0.+0.j], # may vary
            [0.+0.j,  0.+0.j]],
           [[0.+0.j,  0.+0.j],
            [0.+0.j,  0.+0.j]]])

    >>> scipy.fft.rfftn(x, axes=(2, 0))
    array([[[4.+0.j,  0.+0.j], # may vary
            [4.+0.j,  0.+0.j]],
           [[0.+0.j,  0.+0.j],
            [0.+0.j,  0.+0.j]]])