rfftp ============================================== Purpose ---------------- Computes a real 1- or 2-D FFT. Returns the results in a packed format. Format ---------------- .. function:: y = rfftp(x) :param x: data :type x: NxK real matrix or K-length real vector :return y: where :math:L and :math:M are the smallest powers of 2 greater than or equal to :math:N and :math:K, respectively. :rtype y: Lx(M/2+1) matrix or (M/2+1)-length vector Remarks ------- If a dimension of *x* is not a power of 2, it will be padded with zeros to the next allowable size before the FFT is computed. For 1-D FFT's, :func:rfftp returns the positive frequencies in ascending order in the first :math:\frac{M}{2} elements, and the Nyquist frequency in the last element. For 2-D FFT's, :func:rfftp returns the positive and negative frequencies for the row dimension, and for the column dimension, it returns the positive frequencies in ascending order in the first :math:\frac{M}{2} columns, and the Nyquist frequencies in the last column. Usually the FFT of a real function is calculated to find the power density spectrum or to perform filtering on the waveform. In both these cases only the positive frequencies are required. (See also :func:rfft and :func:rfftn for routines that return the negative frequencies as well.) :func:rfftp scales the computed FFT by :math:\frac{1}{L*M}. :func:rfftp uses the Temperton FFT algorithm. .. seealso:: Functions :func:fft, :func:ffti, :func:fftm, :func:fftmi, :func:fftn, :func:rfft, :func:rffti, :func:rfftip, :func:rfftn, :func:rfftnp