add numerical recipes library

lib/nr/k_and_r/recipes/convlv.c

@@ -0,0 +1,34 @@
+
+#include "nrutil.h"
+
+void convlv(data,n,respns,m,isign,ans)
+float ans[],data[],respns[];
+int isign;
+unsigned long m,n;
+{
+	void realft(),twofft();
+	unsigned long i,no2;
+	float dum,mag2,*fft;
+
+	fft=vector(1,n<<1);
+	for (i=1;i<=(m-1)/2;i++)
+		respns[n+1-i]=respns[m+1-i];
+	for (i=(m+3)/2;i<=n-(m-1)/2;i++)
+		respns[i]=0.0;
+	twofft(data,respns,fft,ans,n);
+	no2=n>>1;
+	for (i=2;i<=n+2;i+=2) {
+		if (isign == 1) {
+			ans[i-1]=(fft[i-1]*(dum=ans[i-1])-fft[i]*ans[i])/no2;
+			ans[i]=(fft[i]*dum+fft[i-1]*ans[i])/no2;
+		} else if (isign == -1) {
+			if ((mag2=SQR(ans[i-1])+SQR(ans[i])) == 0.0)
+				nrerror("Deconvolving at response zero in convlv");
+			ans[i-1]=(fft[i-1]*(dum=ans[i-1])+fft[i]*ans[i])/mag2/no2;
+			ans[i]=(fft[i]*dum-fft[i-1]*ans[i])/mag2/no2;
+		} else nrerror("No meaning for isign in convlv");
+	}
+	ans[2]=ans[n+1];
+	realft(ans,n,-1);
+	free_vector(fft,1,n<<1);
+}