Calculates the Fast Fourier transform of a series in polar (Magnitude/Phase) form.
Any series or multi-column table.
Optional. An integer, the FFT length. Defaults
to the length of the input series. If
A complex series or table in Polar form.
W1: gsin(1000, 0.001, 50)
W2: fft(w1, 1024)
W3: fftp(w1, 1024)
Although W2 and W3 are identical in terms of the complex result, W2 contains the FFT result in Cartesian form, a + bi, while W3 represents the result in polar form Meiθ. For plotting purposes, W2 displays the real part of the FFT and W3 displays the magnitude part.
The FFTP result is complex polar and the magnitude of the resultant series is plotted. A mixed radix algorithm is employed to compute the FFT.
FFTP uses the same algorithm as the FFT but is slightly slower because it calculates magnitude/phase.
Use SPECTRUM to produce a normalized magnitude plot.
Oppenheim and Schafer.
Digital Signal Processing
Prentice Hall, 1975
Digital Signal Processing Committee
Programs for Digital Signal Processing
I.E.E.E. Press, 1979