add numerical recipes library

lib/nr/ansi/examples/xrealft.c

@@ -0,0 +1,66 @@
+
+/* Driver for routine realft */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define EPS 1.0e-3
+#define NP 32
+#define WIDTH 50.0
+#define PI 3.1415926
+
+int main(void)
+{
+	int i,j,n=NP/2,nlim;
+	float big,per,scal,small,*data,*size;
+
+	data=vector(1,NP);
+	size=vector(1,NP/2+1);
+	for (;;) {
+		printf("Period of sinusoid in channels (2-%2d)\n",NP);
+		scanf("%f",&per);
+		if (per <= 0.0) break;
+		for (i=1;i<=NP;i++)
+			data[i]=cos(2.0*PI*(i-1)/per);
+		realft(data,NP,1);
+		big = -1.0e10;
+		for (i=2;i<=n;i++) {
+			size[i]=sqrt(SQR(data[2*i-1])+SQR(data[2*i]));
+			if (size[i] > big) big=size[i];
+		}
+		size[1]=fabs(data[1]);
+		if (size[1] > big) big=size[1];
+		size[n+1]=fabs(data[2]);
+		if (size[n+1] > big) big=size[n+1];
+		scal=WIDTH/big;
+		for (i=1;i<=n;i++) {
+			nlim=(int) (0.5+scal*size[i]+EPS);
+			printf("%4d ",i);
+			for (j=1;j<=nlim+1;j++) printf("*");
+			printf("\n");
+		}
+		printf("press RETURN to continue ...\n");
+		(void) getchar();
+		realft(data,NP,-1);
+		big = -1.0e10;
+		small=1.0e10;
+		for (i=1;i<=NP;i++) {
+			if (data[i] < small) small=data[i];
+			if (data[i] > big) big=data[i];
+		}
+		scal=WIDTH/(big-small);
+		for (i=1;i<=NP;i++) {
+			nlim=(int) (0.5+scal*(data[i]-small)+EPS);
+			printf("%4d ",i);
+			for (j=1;j<=nlim+1;j++) printf("*");
+			printf("\n");
+		}
+	}
+	free_vector(size,1,NP/2+1);
+	free_vector(data,1,NP);
+	return 0;
+}
+#undef NRANSI