add numerical recipes library

lib/nr/ansi/examples/xpoidev.c

@@ -0,0 +1,47 @@
+
+/* Driver for routine poidev */
+
+#include <stdio.h>
+#define NRANSI
+#include "nr.h"
+
+#define N 20
+#define NPTS 10000
+#define ISCAL 200
+#define LLEN 50
+
+int main(void)
+{
+	char txt[LLEN+1];
+	long idum=(-13);
+	int i,j,k,klim,dist[N+1];
+	float xm,dd;
+
+	for (;;) {
+		for (j=0;j<=N;j++) dist[j]=0;
+		do {
+			printf("Mean of Poisson distribution (0.0<x<%d.0) ",N);
+			printf("- Negative to end:\n");
+			scanf("%f",&xm);
+		} while (xm > N);
+		if (xm < 0.0) break;
+		for (i=1;i<=NPTS;i++) {
+			j=(int) (0.5+poidev(xm,&idum));
+			if ((j >= 0) && (j <= N)) ++dist[j];
+		}
+		printf("Poisson-distributed deviate, mean %5.2f of %6d points\n",
+			xm,NPTS);
+		printf("%5s %8s %10s\n","x","p(x)","graph:");
+		for (j=0;j<=N;j++) {
+			dd=(float) dist[j]/NPTS;
+			for (k=0;k<=LLEN;k++) txt[k]=' ';
+			klim=(int) (ISCAL*dd);
+			if (klim > LLEN) klim=LLEN;
+			for (k=1;k<=klim;k++) txt[k]='*';
+			txt[LLEN]='\0';
+			printf("%6d %8.4f   %s\n",j,dd,txt);
+		}
+	}
+	return 0;
+}
+#undef NRANSI