--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rDiff/src/locfit/m/backtr.m	Thu Feb 14 23:38:36 2013 -0500
@@ -0,0 +1,33 @@
+function z=backtr(y,fit)
+%
+% Inverse-link transformation of y.
+
+fali = fit.fit_points.family_link;
+link = fali(2);
+switch link
+  case 3
+    z=y;
+  case 4
+    z=exp(y);
+  case 5
+    z = y;
+    i = find(y<=0);
+    if (length(i)>0)
+      z(i) = exp(y(i))./(1+exp(y(i)));
+    end;
+    i = find(y>0);
+    if (length(i)>0)
+      z(i) = 1./(1+exp(-y(i)));
+    end;
+  case 6
+    z=1./y;
+  case 7
+    z=y.*abs(y);
+  case 8
+    z=sin(y).^2;
+  otherwise
+     disp('Backtr: invalid link');
+     z=y;
+end;
+
+return;