add numerical recipes library

lib/nr/ansi/examples/xtwofft.c

@@ -0,0 +1,66 @@
+
+/* Driver for routine twofft */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define N 32
+#define N2 (2*N)
+#define PER 8
+#define PI 3.1415926
+
+void prntft(float data[],unsigned long nn)
+{
+	unsigned long n;
+
+	printf("%4s %13s %13s %12s %13s\n",
+		"n","real(n)","imag.(n)","real(N-n)","imag.(N-n)");
+	printf("   0 %14.6f %12.6f %12.6f %12.6f\n",
+		data[1],data[2],data[1],data[2]);
+	for (n=3;n<=nn+1;n+=2) {
+		printf("%4lu %14.6f %12.6f %12.6f %12.6f\n",
+			((n-1)/2),data[n],data[n+1],
+			data[2*nn+2-n],data[2*nn+3-n]);
+	}
+	printf(" press return to continue ...\n");
+	(void) getchar();
+	return;
+}
+
+int main(void)
+{
+	unsigned long i;
+	int isign;
+	float *data1,*data2,*fft1,*fft2;
+
+	data1=vector(1,N);
+	data2=vector(1,N);
+	fft1=vector(1,N2);
+	fft2=vector(1,N2);
+	for (i=1;i<=N;i++) {
+		data1[i]=floor(0.5+cos(i*2.0*PI/PER));
+		data2[i]=floor(0.5+sin(i*2.0*PI/PER));
+	}
+	twofft(data1,data2,fft1,fft2,N);
+	printf("Fourier transform of first function:\n");
+	prntft(fft1,N);
+	printf("Fourier transform of second function:\n");
+	prntft(fft2,N);
+	/* Invert transform */
+	isign = -1;
+	four1(fft1,N,isign);
+	printf("inverted transform  =  first function:\n");
+	prntft(fft1,N);
+	four1(fft2,N,isign);
+	printf("inverted transform  =  second function:\n");
+	prntft(fft2,N);
+	free_vector(fft2,1,N2);
+	free_vector(fft1,1,N2);
+	free_vector(data2,1,N);
+	free_vector(data1,1,N);
+	return 0;
+}
+#undef NRANSI