TVec.FFT Methods

Summary

Fast Furier Transformation (FFT) from complex to complex or from real to complex.

Class
TVec

Declaration

Function FFT(ConjugateExtend: boolean = false): TVec;

Description

Fast Furier Transformation (FFT) from complex to complex or from real to complex. Calculate the FFT from all calling vector elements in-place. If the calling vector is complex then complex to complex forward FFT is performed. If the calling vector is real then real to complex FFT is performed.

The Length of the transforming vector can be any number but highest performance will be achieved if it is a power of two. NOTE: When performing FFT from real to complex the conjugated symmetric part is also generated by conjugating and mirroring the first half of the spectrum. If Complex is false, the operation will not be performed in-place, if the Length of the destination will allocate more than amount of the memory preallocated for the TVec object. Instead, the data will be copied first to allocate enough space to store the result.

There are two important parameters to consider that affect how will the FFT be computed: FFTStorageFormat and FFTScrambled. The default storage format is fsfCCS.

See Also
FFTFromReal
IFFT
TDenseMtxVec.FFTFromReal
TDenseMtxVec.IFFT
TDenseMtxVec.FFTStorageFormat
TDenseMtxVec.FFTScrambled

Example 1

        var a,b: TVec;
        begin
          CreateIt(a,b);
          try
            a.SetIt(False,[1,2,3,4]);
            b.FFT(a);
            a.FFT;     // a = [(10, 0),( -2,2), (-2, 0), (-2,-2)]
            if not a.Equal(b) then ERaise('Not equal');
          finally
            FreeIt(a,b);
          end;
        end;

Declaration

Function FFT(Vec: TVec; ConjugateExtend: boolean = false): TVec;

Description

Calculate the FFT from all Vec elements and store the results in the calling vector. Vec Length must not be a power of two, but highest performance will be achieved if it is a power of two. Length and Complex properties of the calling vector are set implicitly to match Vec vector. If Vec is complex then complex to complex forward FFT is performed. If Vec is real then real to complex FFT is performed and the conjugate symmetric part is appended.