From d3a7ec6c1d8543c12841a7fd4e969ee7be04ee24 Mon Sep 17 00:00:00 2001
From: Chen Xu <thitchen@users.noreply.github.com>
Date: Wed, 23 Sep 2015 20:31:07 -0700
Subject: [PATCH] in apk, if length of 'actual' is 0, it returns 0

---
 R/R/metrics.r | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/R/R/metrics.r b/R/R/metrics.r
index 3d8ad57..b957542 100644
--- a/R/R/metrics.r
+++ b/R/R/metrics.r
@@ -166,6 +166,10 @@ apk <- function(k, actual, predicted)
 {
     score <- 0.0
     cnt <- 0.0
+    if(length(actual) == 0)
+    {
+    	return(0)
+    }
     for (i in 1:min(k,length(predicted)))
     {
         if (predicted[i] %in% actual && !(predicted[i] %in% predicted[0:(i-1)]))