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78 lines
1.5 KiB
78 lines
1.5 KiB
4 months ago
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/*
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* Experimental data distribution table generator
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* Taken from the uncopyrighted NISTnet code (public domain).
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*
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* Rread in a series of "random" data values, either
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* experimentally or generated from some probability distribution.
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* From this, report statistics.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <malloc.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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void
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stats(FILE *fp)
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{
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struct stat info;
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double *x;
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int limit;
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int n=0, i;
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double mu=0.0, sigma=0.0, sumsquare=0.0, sum=0.0, top=0.0, rho=0.0;
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double sigma2=0.0;
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fstat(fileno(fp), &info);
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if (info.st_size > 0) {
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limit = 2*info.st_size/sizeof(double); /* @@ approximate */
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} else {
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limit = 10000;
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}
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x = (double *)malloc(limit*sizeof(double));
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for (i=0; i<limit; ++i){
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fscanf(fp, "%lf", &x[i]);
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if (feof(fp))
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break;
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sumsquare += x[i]*x[i];
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sum += x[i];
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++n;
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}
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mu = sum/(double)n;
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sigma = sqrt((sumsquare - (double)n*mu*mu)/(double)(n-1));
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for (i=1; i < n; ++i){
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top += ((double)x[i]-mu)*((double)x[i-1]-mu);
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sigma2 += ((double)x[i-1] - mu)*((double)x[i-1] - mu);
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}
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rho = top/sigma2;
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printf("mu = %12.6f\n", mu);
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printf("sigma = %12.6f\n", sigma);
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printf("rho = %12.6f\n", rho);
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/*printf("sigma2 = %10.4f\n", sqrt(sigma2/(double)(n-1)));*/
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/*printf("correlation rho = %10.6f\n", top/((double)(n-1)*sigma*sigma));*/
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}
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int
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main(int argc, char **argv)
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{
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FILE *fp;
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if (argc > 1) {
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fp = fopen(argv[1], "r");
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if (!fp) {
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perror(argv[1]);
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exit(1);
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}
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} else {
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fp = stdin;
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}
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stats(fp);
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return 0;
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}
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