#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>

/***************************************************/
/***     Make magnitude only file	      **/
/***     FFT format data files only, Magnitudes only *****/
/***************************************************/

void main(int argc, char *argv[]) {
    FILE *file_in,*file_out;
    float *data,*output;
    float temp, mag,  phase;
    float PI = 4.*atan( 1. ) ;
    long i, j, length, num_files;
    
    if (argc != 3)        {
        printf("useage: subtract infile.fft outfile.fft\n");
        exit(0);
    }
    file_in = fopen(argv[1],"rb");
    if (file_in)   {
        j = 0;
        while (fread(&temp,4,1,file_in)) j++;
    }
    else {
        printf("File Problems!!\n");
        exit(0);
    }
    length = j;
    fseek(file_in, 0, 0);
    data = (float *) malloc(4 * length);
    fread(data,4,i,file_in);
    fclose(file_in);

    file_out = fopen(argv[2],"wb");
    output = (float *) malloc(4 * length);
    output[0] = fabs(data[0]);
    output[1] = fabs(data[1]);
    for (j=2;j<length;j+=2) {
/*        output[j] = data[j] - data2[j];
//        output[j+1] = data[j+1] - data2[j+1];
*/
	mag = sqrt(data[j]*data[j] 
                    + data[j+1]*data[j+1]);
        output[j] = mag;
	output[j+1] = 0;
/*        output[j] = mag;
//
*/        output[j+1] = mag * sin(phase);
    }
    fwrite(output,4,length,file_out); 
    
    free(data);
    free(output);
    fclose(file_out);
}