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77 lines
1.5 KiB
77 lines
1.5 KiB
/* |
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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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