Autocorrelation

Calculates the autocorrelation of the elements from the floatvalue array.

Usage: autocorrelation($<$lag$>$ [,$<$start$>$])

where $<$lag$>$ is the maximum autocorrelation lag that will be computed; and [,$<$start$>$] is an optional parameter that specifies the position, in the floatvalue array, from which to start calculating the autocorrelation. If this parameter is not specified, the calculation will start from the beginning of the array.