# fft_fft_multiple_real

## Description

computes the discrete Fourier transforms of iSequences sequences of iSize real data values. For forward FT, each output sequence is in Hermitian form; For backward FT, each input sequence is in Hermitian form.

## Syntax

int fft_fft_multiple_real( int iSequences, int iSize, double * vSig, FFT_SIGN iSign = FFT_FORWARD )


## Parameters

iSequences
[input] the number of sequences.
iSize
[input] the number of data values in each sequence.
vSig
[modify] the input data sequences to be transformed, and the result of the Fourier transforms.
iSign
[input] the transformation to carry out
= FFT_FORWARD: FFT (by default)
= FFT_BACKWARD: IFFT.

## Return

Returns 0 for success or error codes for failure.

## Examples

EX1

//Assume the current Worksheet has 3 sequences of real data values stored in the first
//column successively. This piece of code computers the discrete Fourier transform.
//The result is output into the second column. An inverse transform is performed,
//and the result is output into the third column.

#include <..\originlab\fft.h>
void TEST_fft_fft_multiple_real()
{
int iSeq=3, iL=7, success;
int n = iSeq*iL;
Worksheet wks = Project.ActiveLayer();
if(wks)
{
Dataset xx(wks, 0);
Dataset aa(wks, 1);
aa.SetSize(n);
Dataset bb(wks, 2);
bb.SetSize(n);

vector x = xx;

///FT
success = fft_fft_multiple_real(iSeq, iL, x);
aa = x;

///IFT
success = fft_fft_multiple_real(iSeq, iL, x, FFT_BACKWARD);
bb = x;
}
}