correl.cpp

此程序为VC++常用数值算法这本书附赠的光盘中包含了本书中全部的源代码

void correl(double data1[], double data2[], int &n,double ans[])
{
	int no2,i,temp;
    double fft[129],dum,dum1,dum2;
	for(i=1; i<=128; i++)
		fft[i]=0.0;
	temp=-1;
    twofft(data1, data2, fft, ans, n);
    no2 = n / 2.0;
    for (i = 1; i<=no2 + 1; i++)
	{
      dum = ans[2 * i - 1];
      dum1 = fft[2 * i - 1] * dum + fft[2 * i] * ans[2 * i];
      ans[2 * i - 1] = dum1 / float(no2);
      dum2 = fft[2 * i] * dum - fft[2 * i - 1] * ans[2 * i];
      ans[2 * i] = dum2 / float(no2);
    }
    ans[2] = ans[n + 1];
    realft(ans, no2,temp);
    for(i=1; i<=128; i++)
		fft[i]=0.0;
}