Description

S3L_acorr computes the 1D or 2D autocorrelation of a signal represented by the parallel array described by S3L array handle a. The result is stored in the parallel array described by the S3L array handle c.

a and c are of the same real or complex type.

For the 1D case, if a is of length ma, the result of the autocorrelation will be of length 2*ma-1. In the 2D case, if a is of size [ma,na], the result of the autocorrelation is of size [2*ma-1,2*na-1].

The size of c has to be at least equal to the size of the autocorrelation for each case, as described above. If it is larger, the excess elements of c will contain zero or non-significant entries.

The result of the autocorrelation of a is stored in wrap-around order along each dimension. If the extent of c along a given axis is lc, the autocorrelation at zero lag is stored in c(0), the autocorrelation at lag 1 in c(1), and so forth. The autocorrelation at lag -1 is stored in c(lc-1), the autocorrelation at lag -2 is stored in c(lc-2), and so forth.

Side Effects

Following calculation of the autocorrelation of a, a may be destroyed, since it is used internally as auxiliary storage. If its contents will be reused after autocorrelation is performed, first copy it to a temporary array.

S3L_acorr is most efficient when all arrays have the same length and when this length is one that can be computed efficiently via S3L_fft, or S3L_rc_fft. See "S3L_fft " and "S3L_rc_fft and S3L_cr_fft " for more information about execution efficiency.

Restriction

The dimensions of array c must be such that a 1D or 2D complex-to-complex FFT or real-to-complex FFT can be computed.