Performs N-D FFT interpolation any data for which fftn works. Will upsample by zero-filling, downsample by truncating high frequencies, or combine both up- and downsampling by dimension to allow arbitrary reshaping.-Performs N-D FFT interpolation on any data for which fftn works. Will upsample by zero-filling, downsample by truncating high frequencies, or combine both up- and downsampling by dimension to allow arbitrary reshaping.