add numerical recipes library

lib/nr/ansi/examples/xgamdev.c

@@ -0,0 +1,47 @@
+
+/* Driver for routine gamdev */
+
+#include <stdio.h>
+#define NRANSI
+#include "nr.h"
+
+#define N 20
+#define NPTS 10000
+#define ISCAL 200
+#define LLEN 50
+
+int main(void)
+{
+	char words[LLEN+1];
+	long idum=(-13);
+	int i,ia,j,k,klim,dist[N+1];
+	float dd;
+
+	for (;;) {
+		for (j=0;j<=N;j++) dist[j]=0;
+		do {
+			printf("Select order of Gamma distribution (n=1..%d), -1 to end\n",N);
+			scanf("%d",&ia);
+		} while (ia > N);
+		if (ia < 0) break;
+		for (i=1;i<=NPTS;i++) {
+			j=(int) gamdev(ia,&idum);
+			if ((j >= 0) && (j <= N)) ++dist[j];
+		}
+		printf("\ngamma-distribution deviate, order %2d of %6d points\n",
+			ia,NPTS);
+		printf("%6s %7s %9s \n","x","p(x)","graph:");
+		for (j=0;j<N;j++) {
+			dd=(float) dist[j]/NPTS;
+			for (k=1;k<=50;k++) words[k]=' ';
+			klim=(int) (ISCAL*dd);
+			if (klim > LLEN) klim=LLEN;
+			for (k=1;k<=klim;k++) words[k]='*';
+			printf("%6d %8.4f  ",j,dd);
+			for (k=1;k<=klim;k++) printf("%c",words[k]);
+			printf("\n");
+		}
+	}
+	return 0;
+}
+#undef NRANSI