rlm@8: #include <stdio.h>
rlm@8: #include <stdlib.h>
rlm@8: #include <math.h>
rlm@8: 
rlm@8: 
rlm@8: int DFT(int dir,int m,double *x1,double *y1)
rlm@8: {
rlm@8:    long i,k;
rlm@8:    double arg;
rlm@8:    double cosarg,sinarg;
rlm@8:    double *x2=NULL,*y2=NULL;
rlm@8: 
rlm@8:    x2 = (double *)(malloc(m*sizeof(double)));
rlm@8:    y2 = (double *)(malloc(m*sizeof(double)));
rlm@8:    if (x2 == NULL || y2 == NULL)
rlm@8:       return 0;
rlm@8: 
rlm@8:    for (i=0;i<m;i++) {
rlm@8:       x2[i] = 0;
rlm@8:       y2[i] = 0;
rlm@8:       arg = - dir * 2.0 * 3.141592654 * (double)i / (double)m;
rlm@8:       for (k=0;k<m;k++) {
rlm@8:          cosarg = cos(k * arg);
rlm@8:          sinarg = sin(k * arg);
rlm@8:          x2[i] += (x1[k] * cosarg - y1[k] * sinarg);
rlm@8:          y2[i] += (x1[k] * sinarg + y1[k] * cosarg);
rlm@8:       }
rlm@8:    }
rlm@8: 
rlm@8:    /* Copy the data back */
rlm@8:    if (dir == 1) {
rlm@8:       for (i=0;i<m;i++) {
rlm@8:          x1[i] = x2[i];
rlm@8:          y1[i] = y2[i];
rlm@8:       }
rlm@8:    } else {
rlm@8:       for (i=0;i<m;i++) {
rlm@8:          x1[i] = x2[i];
rlm@8:          y1[i] = y2[i];
rlm@8:       }
rlm@8:    }
rlm@8: 
rlm@8:    free(x2);
rlm@8:    free(y2);
rlm@8:    return 1;
rlm@8: }