fft ============================================== Purpose ---------------- Computes a 1- or 2-D Fast Fourier transform. Format ---------------- .. function:: y = fft(x) :param x: The values used to compute the Fast Fourier transform. :type x: NxK matrix :return y: where *L* and *M* are the smallest powers of 2 greater than or equal to *N* and *K*, respectively. :rtype y: LxM matrix Examples ---------------- This is example uses the FFT to find the frequency component of a signal buried in a noise. The first section sets up the parameters for the signal of sampling frequency 1 kHz and a signal duration of 1.5 secs :: // Sampling frequency Fs = 1000; // Sampling period big_T = 1/Fs; // Length of signal L = 1500; // Time vector t = seqa(0, big_T, L); Now form the signal given by .. math:: 0.7*sin(2\pi50t) + sin(2\pi120t) :: // Compute signal s = 0.7*sin(2*pi*50*t) + sin(2*pi*120*t); Corrupt the signal with zero-mean white noise: :: // Add white noise x = s + 2*rndn(L,1); Finally, compute the Fourier transform: :: // Compute Fourier transform y = fft(x); Remarks ------- This computes the FFT of *x*, scaled by :math:1/N. This uses a Temperton Fast Fourier algorithm. If *N* or *K* is not a power of 2, *x* will be padded out with zeros before computing the transform. .. seealso:: Functions :func:ffti, :func:rfft, :func:rffti