add numerical recipes library

lib/nr/ansi/recipes/chixy.c

@@ -0,0 +1,30 @@
+
+#include <math.h>
+#define NRANSI
+#include "nrutil.h"
+#define BIG 1.0e30
+
+extern int nn;
+extern float *xx,*yy,*sx,*sy,*ww,aa,offs;
+
+float chixy(float bang)
+{
+	int j;
+	float ans,avex=0.0,avey=0.0,sumw=0.0,b;
+
+	b=tan(bang);
+	for (j=1;j<=nn;j++) {
+		ww[j] = SQR(b*sx[j])+SQR(sy[j]);
+		sumw += (ww[j] = (ww[j] < 1.0/BIG ? BIG : 1.0/ww[j]));
+		avex += ww[j]*xx[j];
+		avey += ww[j]*yy[j];
+	}
+	avex /= sumw;
+	avey /= sumw;
+	aa=avey-b*avex;
+	for (ans = -offs,j=1;j<=nn;j++)
+		ans += ww[j]*SQR(yy[j]-aa-b*xx[j]);
+	return ans;
+}
+#undef BIG
+#undef NRANSI