Calculates the fast Fourier transform of the signal as stored in the array parameters DataReal and DataImag. The length of both arrays has to be a power of two. Before the transformation takes place the signal is weighted by a function specified by the parameter Weighting. Version  allows to pass a value in the parameter param which is interpreted as alpha of the Tukey window if Weighting = fwTukey, otherwise it is ignored. The valid range for alpha is 0...1 and is automatically confined to this range. For version  the Tukey alpha parameter is set internally to a value of 0.5.
The result of the transformation replaces the original data in the arrays DataReal and DataImag. The following figure clarifies the situation:
The function returns the following error codes:
0 ... everything is OK
-1 ... the size of the data array is not a power of 2
-2 ... the real and imaginary parts are not of the same size