Dataset TOF(wksData,wksData.Columns("TOF").GetIndex());
	Dataset PHonIon(wksData,wksData.Columns("PHonIon").GetIndex());
	Dataset PHoffIon(wksData,wksData.Columns("PHoffIon").GetIndex());
	Dataset PHonIoff(wksData,wksData.Columns("PHonIoff").GetIndex());
	Dataset Signal(wksData,wksData.Columns("Signal").GetIndex());
	Dataset FFTtof(wksData,wksData.Columns("FFTtof").GetIndex());
	Dataset FFTsig(wksData,wksData.Columns("FFTsig").GetIndex());
	
	int npts = PHonIon.GetSize();
	Signal.SetSize(npts);

	int nptsFFT = 1;
	while (nptsFFT<npts) nptsFFT*=2; // FFT requires the number of points being equal a power of 2
	vector FFTx, FFTy;
    FFTtof.SetSize(nptsFFT);
    FFTsig.SetSize(nptsFFT);
    
	for (int n=0; n<npts; n++)
	{
		Signal[n] = -PHonIon[n]+PHoffIon[n]+PHonIoff[n]; // these are the data to be filtered
		FFTtof[n] = TOF[n];
		FFTsig[n] = Signal[n];
	}
	double dt = TOF[1]-TOF[0];
	for (n=npts;n<nptsFFT;n++)
	{
		FFTtof[n] = FFTtof[n-1]+dt;
		FFTsig[n] = 0.0;
	}

	Curve FFTcurve(FFTtof,FFTsig);
    int ierr = fft_lowpass(FFTcurve,2e7);
    if (ierr>0)
    {
    	string messagestr;
    	messagestr.Format("ERROR: FFT returned error code %d",ierr);
    	MessageBox(NULL,messagestr);
    }    
    FFTtof.SetSize(npts);
    FFTsig.SetSize(npts);

int fft_lowpass(Curve& crvSignal, double dFc);
int fft_lowpass(vector& vecSignal, double dFc, vector* vecTime=NULL);