irfftn#
- scipy.fft.irfftn(x, s=None, axes=None, norm=None, overwrite_x=False, workers=None, *, plan=None)[source]#
- Computes the inverse of - rfftn- This function computes the inverse of the N-D discrete Fourier Transform for real input over any number of axes in an M-D array by means of the Fast Fourier Transform (FFT). In other words, - irfftn(rfftn(x), x.shape) == xto within numerical accuracy. (The- a.shapeis necessary like- len(a)is for- irfft, and for the same reason.)- The input should be ordered in the same way as is returned by - rfftn, i.e., as for- irfftfor the final transformation axis, and as for- ifftnalong all the other axes.- Parameters:
- xarray_like
- Input array. 
- ssequence of ints, optional
- Shape (length of each transformed axis) of the output ( - s[0]refers to axis 0,- s[1]to axis 1, etc.). s is also the number of input points used along this axis, except for the last axis, where- s[-1]//2+1points of the input are used. Along any axis, if the shape indicated by s 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. Except for the last axis which is taken to be- 2*(m-1), where- mis the length of the input along that axis.
- axessequence of ints, optional
- Axes over which to compute the inverse 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_xbool, optional
- If True, the contents of x can be destroyed; the default is False. See - fftfor more details.
- workersint, optional
- Maximum number of workers to use for parallel computation. If negative, the value wraps around from - os.cpu_count(). See- fftfor more details.
- planobject, optional
- This argument is reserved for passing in a precomputed plan provided by downstream FFT vendors. It is currently not used in SciPy. - Added in version 1.5.0. 
 
- Returns:
- outndarray
- The truncated or zero-padded input, transformed along the axes indicated by axes, or by a combination of s or x, as explained in the parameters section above. The length of each transformed axis is as given by the corresponding element of s, or the length of the input in every axis except for the last one if s is not given. In the final transformed axis the length of the output when s is not given is - 2*(m-1), where- mis the length of the final transformed axis of the input. To get an odd number of output points in the final axis, s must be specified.
 
- Raises:
- ValueError
- If s and axes have different length. 
- IndexError
- If an element of axes is larger than the number of axes of x. 
 
 - See also - Notes - See - fftfor definitions and conventions used.- See - rfftfor definitions and conventions used for real input.- The default value of s assumes an even output length in the final transformation axis. When performing the final complex to real transformation, the Hermitian symmetry requires that the last imaginary component along that axis must be 0 and so it is ignored. To avoid losing information, the correct length of the real input must be given. - Examples - >>> import scipy.fft >>> import numpy as np >>> x = np.zeros((3, 2, 2)) >>> x[0, 0, 0] = 3 * 2 * 2 >>> scipy.fft.irfftn(x) array([[[1., 1.], [1., 1.]], [[1., 1.], [1., 1.]], [[1., 1.], [1., 1.]]])