1 /* 2 * Experimental data distribution table generator 3 * Taken from the uncopyrighted NISTnet code (public domain). 4 * 5 * Rread in a series of "random" data values, either 6 * experimentally or generated from some probability distribution. 7 * From this, report statistics. 8 */ 9 10 #include <stdio.h> 11 #include <stdlib.h> 12 #include <math.h> 13 #include <malloc.h> 14 #include <sys/types.h> 15 #include <sys/stat.h> 16 17 void 18 stats(FILE *fp) 19 { 20 struct stat info; 21 double *x; 22 int limit; 23 int n=0, i; 24 double mu=0.0, sigma=0.0, sumsquare=0.0, sum=0.0, top=0.0, rho=0.0; 25 double sigma2=0.0; 26 27 fstat(fileno(fp), &info); 28 if (info.st_size > 0) { 29 limit = 2*info.st_size/sizeof(double); /* @@ approximate */ 30 } else { 31 limit = 10000; 32 } 33 x = (double *)malloc(limit*sizeof(double)); 34 35 for (i=0; i<limit; ++i){ 36 fscanf(fp, "%lf", &x[i]); 37 if (feof(fp)) 38 break; 39 sumsquare += x[i]*x[i]; 40 sum += x[i]; 41 ++n; 42 } 43 mu = sum/(double)n; 44 sigma = sqrt((sumsquare - (double)n*mu*mu)/(double)(n-1)); 45 46 for (i=1; i < n; ++i){ 47 top += ((double)x[i]-mu)*((double)x[i-1]-mu); 48 sigma2 += ((double)x[i-1] - mu)*((double)x[i-1] - mu); 49 50 } 51 rho = top/sigma2; 52 53 printf("mu = %12.6f\n", mu); 54 printf("sigma = %12.6f\n", sigma); 55 printf("rho = %12.6f\n", rho); 56 /*printf("sigma2 = %10.4f\n", sqrt(sigma2/(double)(n-1)));*/ 57 /*printf("correlation rho = %10.6f\n", top/((double)(n-1)*sigma*sigma));*/ 58 } 59 60 61 int 62 main(int argc, char **argv) 63 { 64 FILE *fp; 65 66 if (argc > 1) { 67 fp = fopen(argv[1], "r"); 68 if (!fp) { 69 perror(argv[1]); 70 exit(1); 71 } 72 } else { 73 fp = stdin; 74 } 75 stats(fp); 76 return 0; 77 } 78
