Add example for regional frequency distribution

Change-Id: I5cc2f31baae86ccba1eb73a4b0bb76d0fbfaba1c
diff --git a/.gitignore b/.gitignore
index 5b6a065..f51ef92 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 .Rhistory
 .RData
 .Ruserdata
+cache/