TVec.IFFTToReal Method (boolean)

The inverse FFT from complex to real.

Pascal

function IFFTToReal(NoScale: boolean = False): TVec; overload;

Calculates the inverse Fast Fourier Transformation (FFT) from complex to real from all calling vector elements. The result is a real type vector. Input vector must be a complex vector or an exception is raised. If the NoScale parameter is true then no scaling is performed for the calling vector. The results can be erroneous if overflow or underflow occurs.

In-place fsfCCS complication

When TDenseMtxVec.FFTStorageFormat is equal to fsfCCS the Length of the result will be equal to Length-2, because the source data is bigger than the result data by 2 real samples, if TDenseMtxVec.FFTOddLength is false. If TDenseMtxVec.FFTOddLength is True the result will fill up Length-1 samples.

Example

var a,b: TVec; begin CreateIt(a,b); try //Even a.SetIt(True,[1,2,3,4]); b.FFTFromReal(a); // b = [(10, 0),( -2,2), (-2, 0)] b.IFFTToReal; // b = [1, 2, 3, 4, -2, 0)] //Odd length a.SetIt(True,[1,2,3,0]); b.FFTOddLength := True; //use only Length-1 samples b.FFTFromReal(a); // b = [(6,0),( -1.5,0.8660)] //result requires 2 complex (= 4 real numbers) b.IFFTToReal; //b = [1, 2, 3, 0.8660] //Event length a.SetIt(True,[1,2,3,4, 0,0]); //allocate two more elements a.FFTOddLength := false; //use only Length-2 samples a.FFTFromReal; // a = [(10, 0),( -2,2), (-2, 0)] //result requires 3 complex (= 6 real numbers) a.IFFToReal; // a = [1, 2, 3, 4, -2, 0)] finally FreeIt(a,b); end; end;

TVec Class, TVec Members, MtxVec Namespace, IFFTToReal Method, Example, See Also

What do you think about this topic? Send feedback!