xsinft.cpp

这是数学计算上常用的计算方法

#include <iostream>
#include <iomanip>
#include <cmath>
#include "nr.h"
using namespace std;

// Driver for routine sinft

int main(void)
{
        const int NP=16;
        const DP EPS=1.0e-3, WIDTH=30.0, PI=3.141592653589793238;
        int i,j,nlim;
        DP big,per,scal,small;
        Vec_DP data(NP);

        for (;;) {
          cout << endl << "Period of sinusoid in channels (3-";
          cout << NP << ", or 0 to end) " << endl;
          cin >> per;
          cin.get();
          if (per <= 0.0) break;
          for (i=0;i<NP;i++) data[i]=sin(2.0*PI*i/per);
          NR::sinft(data);
          big = -1.0e10;
          small=1.0e10;
          for (i=0;i<NP;i++) {
            if (data[i] < small) small=data[i];
            if (data[i] > big) big=data[i];
          }
          scal=WIDTH/(big-small);
          for (i=0;i<NP;i++) {
            nlim=int(scal*(data[i]-small)+EPS+0.5);
            cout << setw(4) << i << " ";
            for (j=0;j<nlim+1;j++) cout << "*";
            cout << endl;
          }
          cout << "press RETURN to continue ..." << endl;
          cin.get();
          NR::sinft(data);
          big = -1.0e10;
          small=1.0e10;
          for (i=0;i<NP;i++) {
            if (data[i] < small) small=data[i];
            if (data[i] > big) big=data[i];
          }
          scal=WIDTH/(big-small);
          for (i=0;i<NP;i++) {
            nlim=int(scal*(data[i]-small)+EPS+0.5);
            cout << setw(4) << i << " ";
            for (j=0;j<nlim+1;j++) cout << "*";
            cout << endl;
          }
        }
        return 0;
}