1 files changed, 78 insertions, 0 deletions
diff --git a/netem/stats.c b/netem/stats.c
new file mode 100644
index 0000000..99c4fee
--- /dev/null
+++ b/netem/stats.c
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: NIST-PD */
+/*
+ * Experimental data  distribution table generator
+ * Taken from the uncopyrighted NISTnet code (public domain).
+ *
+ * Rread in a series of "random" data values, either
+ * experimentally or generated from some probability distribution.
+ * From this, report statistics.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <malloc.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+void
+stats(FILE *fp)
+{
+	struct stat info;
+	double *x;
+	int limit;
+	int n=0, i;
+	double mu=0.0, sigma=0.0, sumsquare=0.0, sum=0.0, top=0.0, rho=0.0;
+	double sigma2=0.0;
+
+	fstat(fileno(fp), &info);
+	if (info.st_size > 0) {
+		limit = 2*info.st_size/sizeof(double);	/* @@ approximate */
+	} else {
+		limit = 10000;
+	}
+	x = (double *)malloc(limit*sizeof(double));
+
+	for (i=0; i<limit; ++i){
+		fscanf(fp, "%lf", &x[i]);
+		if (feof(fp))
+			break;
+		sumsquare += x[i]*x[i];
+		sum += x[i];
+		++n;
+	}
+	mu = sum/(double)n;
+	sigma = sqrt((sumsquare - (double)n*mu*mu)/(double)(n-1));
+
+	for (i=1; i < n; ++i){
+		top += ((double)x[i]-mu)*((double)x[i-1]-mu);
+		sigma2 += ((double)x[i-1] - mu)*((double)x[i-1] - mu);
+
+	}
+	rho = top/sigma2;
+
+	printf("mu =    %12.6f\n", mu);
+	printf("sigma = %12.6f\n", sigma);
+	printf("rho =   %12.6f\n", rho);
+	/*printf("sigma2 = %10.4f\n", sqrt(sigma2/(double)(n-1)));*/
+	/*printf("correlation rho = %10.6f\n", top/((double)(n-1)*sigma*sigma));*/
+}
+
+
+int
+main(int argc, char **argv)
+{
+	FILE *fp;
+
+	if (argc > 1) {
+		fp = fopen(argv[1], "r");
+		if (!fp) {
+			perror(argv[1]);
+			exit(1);
+		}
+	} else {
+		fp = stdin;
+	}
+	stats(fp);
+	return 0;
+}