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|
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <stdio_ext.h>
#define PI 3.1415926535897932
#define NULL 0
#define EQUA1 1
#define EQUA2 2
#define EQUA3 3
void SWAP(double* i, double* j);
void four1(double *data, const int n, const int isign);
void whichequa (double* p,int n);
int valid_input2(int* p);
int valid_input(double* p);
void result(double *data2,int n); ;
int main(int argc, char* argv[])
{
int j,n=256,isign=1; //256 complex components, e.g.
double data2[512]; //tableau de taille 2*n
whichequa(data2,n);
result(data2,n);
four1(data2,n,isign);
isign=-1;
four1(data2,n,isign);
result(data2,n);
return (0);
}
//___________________________________________________________________
void four1(double *data, const int n, const int isign)
{
/*Replaces data[0..2*n-1] by its discrete Fourier transform, if isign is input as 1; or replaces
data[0..2*n-1] by n times its inverse discrete Fourier transform, if isign is input as 1. data
is a complex array of length n stored as a real array of length 2*n. n must be an integer power
of 2. */
int nn,mmax,m,j,istep,i;
double wtemp,wr,wpr,wpi,wi,theta,tempr,tempi;
if (n<2 || n&(n-1)) printf("n must be power of 2 in four1");
nn = n << 1;
j = 1;
for (i=1;i<nn;i+=2)
{ //This is the bit-reversal section of the
if (j > i) //routine.
{
//printf("data[j-1]:%lf\ndata[i-1]:%lf\n",data[j-1],data[i-1]);
SWAP(&data[j-1],&data[i-1]); //Exchange the two complex numbers.
//printf("data[j-1]:%lf\ndata[i-1]:%lf\n",data[j-1],data[i-1]);
SWAP(&data[j],&data[i]);
}
m=n;
while (m >= 2 && j > m)
{
j -= m;
m >>= 1;
}
j += m;
}
//Here begins the Danielson-Lanczos section of the routine.
mmax=2;
while (nn > mmax)
{ //Outer loop executed log2 n times.
istep=mmax << 1;
theta=isign*(6.28318530717959/mmax); //Initialize the trigonometric recurrence.
wtemp=sin(0.5*theta);
wpr = -2.0*wtemp*wtemp;
wpi=sin(theta);
wr=1.0;
wi=0.0;
for (m=1;m<mmax;m+=2) //Here are the two nested inner loops.
{
for (i=m;i<=nn;i+=istep)
{
j=i+mmax; //This is the Danielson-Lanczos for-mula:
tempr=wr*data[j-1]-wi*data[j];
tempi=wr*data[j]+wi*data[j-1];
data[j-1]=data[i-1]-tempr;
data[j]=data[i]-tempi;
data[i-1] += tempr;
data[i] += tempi;
}
wr=(wtemp=wr)*wpr-wi*wpi+wr; //Trigonometric recurrence.
wi=wi*wpr+wtemp*wpi+wi;
}
mmax=istep;
}
}
//___________________________________________________________________
void whichequa (double* data2,int n)
{
int equa_type,j,valid;
double P,w1=0,FI1=0,w2=0,FI2=0;
do
{
printf("which equation do you want ? (1) (2) (3)\n") ;
valid=valid_input2(&equa_type);
} while (!valid);
switch(equa_type)
{
case EQUA1:
printf("enter a value for w1\n") ;
valid=valid_input(&w1);
printf("enter a value for FI1\n") ;
valid=valid_input(&FI1);
printf("enter a value for w2\n") ;
valid=valid_input(&w2);
printf("enter a value for FI2\n") ;
valid=valid_input(&FI2);
for (j=0;j<(2*n);j+=2)
{
if ((0<=j) && (j<=20)) data2[j] = sin(w1*j+FI1)+sin(w2*j+FI2) ;
else data2[j]=0;
}
for (j=1;j<(2*n);j+=2)
data2[j]=0;
break;
case EQUA2:
P=0; FI1=50;
for (j=0;j<n;j++)
{
data2[2*j] = cos(2*PI/n*FI1*j+P);
data2[2*j+1] = sin(2*PI/n*FI1*j+P);
}
break;
case EQUA3:
break;
}
}
//___________________________________________________________________
int valid_input2(int* p)
{
int quit=0,valid,x;
char chaine[20] = "";
fgets(chaine, sizeof(chaine), stdin);
__fpurge(stdin); /* Purge the buffer to prevent reds of any remaining characters */
quit=(chaine[0]=='q')||(chaine[0]=='Q');
if (quit)
{
printf("You have quit this application.\n") ;
exit(EXIT_SUCCESS) ;
}
valid=sscanf(chaine, "%d", &x);
if (!valid) printf("illegal character(s) in input. Please, try again\n");
if((x>3)&&(valid))
{
printf("this value of x is too big. x must be under 3. Please, try again\n");
valid=0;
}
*p=x;
return valid;
}
//___________________________________________________________________
int valid_input(double* p)
{
int quit=0,valid;
double x;
char chaine[20] = "";
do
{
fgets(chaine, sizeof(chaine), stdin);
__fpurge(stdin); /* Purge the buffer to prevent reds of any remaining characters */
quit=(chaine[0]=='q')||(chaine[0]=='Q');
if (quit)
{
printf("You have quit this application.\n") ;
exit(EXIT_SUCCESS) ;
}
valid=sscanf(chaine, "%lf", &x);
if (!valid) printf("illegal character(s) in input. Please, try again\n");
} while (!valid);
*p=x;
return valid;
}
//___________________________________________________________________
void result (double* data2,int n)
{
int i=0;
FILE* fichier = NULL;
fichier = fopen("refft.txt","w+");
if (fichier != NULL)
{
for (i=0;i<(2*n);i+=2)
{
fprintf (fichier, "%d %f\n",i/2,data2[i]);
}
fclose (fichier);
}
else
{
printf("Impossible d'ouvrir le fichier test.txt");
}
fichier = fopen("imfft.txt","w+");
for (i=1;i<(2*n);i+=2)
{
fprintf (fichier, "%d %f\n",(i-1)/2,data2[i]);
}
fclose (fichier);
}
//___________________________________________________________________
void SWAP(double* i, double* j) {
double t = *i;
//t = *i;
*i = *j;
*j=t;
} |
fft, numerical recipie
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