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Discrete Prolate Spheroidal Sequences
Syntax dpss(Nmw)
See Also fspec

Returns discrete prolate spheroidal sequences, where N an integer scalar specifying the number of points in each sequence, m is an integer scalar specifying the number of sequences to return, and w is a real or double-precision scalar specifying the fractional bandwidth of the sequences such that 0 < w < .5, with a suggested value of 4./N. The sequence of order i is placed in the (i+1)-th column of the return value for i = 0, ... , m - 1. The return value has m columns, N rows, and the same type as w.

These sequences are used as tapers for spectral estimation (see fspec ). There are two important factors corresponding to a taper: its bandwidth (how wide a frequency range it allows leakage over) and its rejection (how much energy is reduced when it is outside that frequency range). If w is small, the frequency range of the allowed leakage will be small. On the other hand, a smaller w leads to more energy leaking outside the allowed range (poorer rejection).

     N = 128
     m = 1
     w = 4d0 / N
     S = dpss(N, m, w)
     gtitle("Discrete Prolate Spheroidal Window")
     gplot(seq(N)/double(N), S)
returns the following plot: