From 870bcdceb64d7ebcf96f33e1c3d89eb1ec3bbd8a Mon Sep 17 00:00:00 2001
From: kortschak <dan.kortschak@adelaide.edu.au>
Date: Tue, 30 Jan 2018 02:22:43 +1030
Subject: [PATCH] stat: fix ROC for uniform cases

---
 stat/roc.go | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/stat/roc.go b/stat/roc.go
index 1ddd34c1..b6785661 100644
--- a/stat/roc.go
+++ b/stat/roc.go
@@ -108,8 +108,13 @@ func ROC(n int, y []float64, classes []bool, weights []float64) (tpr, fpr []floa
 		fpr = fpr[:(bin + 1)]
 	}
 
-	invNeg := 1 / nNeg
-	invPos := 1 / nPos
+	var invNeg, invPos float64
+	if nNeg != 0 {
+		invNeg = 1 / nNeg
+	}
+	if nPos != 0 {
+		invPos = 1 / nPos
+	}
 	for i := range tpr {
 		tpr[i] *= invPos
 		fpr[i] *= invNeg