From 2e383da0d806c638988de15e958720fdbb71f444 Mon Sep 17 00:00:00 2001
From: Evert Timberg <evert.timberg@gmail.com>
Date: Mon, 18 May 2015 08:51:13 -0400
Subject: [PATCH] Handle the beginAtZero option for a linear scale. Added a
 helper for Math.sign

---
 src/Chart.Core.js  | 11 +++++++++++
 src/Chart.Scale.js | 11 ++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/Chart.Core.js b/src/Chart.Core.js
index f60d7c2e7..e5bfd2af3 100755
--- a/src/Chart.Core.js
+++ b/src/Chart.Core.js
@@ -327,6 +327,17 @@
         min = helpers.min = function(array) {
             return Math.min.apply(Math, array);
         },
+		sign = helpers.sign = function(x) {
+			if (Math.sign) {
+				return Math.sign(x);
+			} else {
+				x = +x; // convert to a number
+				if (x === 0 || isNaN(x)) {
+					return x;
+				}
+				return x > 0 ? 1 : -1;
+			}
+		},
         cap = helpers.cap = function(valueToCap, maxValue, minValue) {
             if (isNumber(maxValue)) {
                 if (valueToCap > maxValue) {
diff --git a/src/Chart.Scale.js b/src/Chart.Scale.js
index 1f2ae8779..c991dfea4 100644
--- a/src/Chart.Scale.js
+++ b/src/Chart.Scale.js
@@ -348,7 +348,16 @@
 				// do nothing since that would make the chart weird. If the user really wants a weird chart
 				// axis, they can manually override it
 				if (this.options.beginAtZero) {
-					this.min = Math.min(this.min, 0);
+					var minSign = helpers.sign(this.min);
+					var maxSign = helpers.sign(this.max);
+					
+					if (minSign < 0 && maxSign < 0) {
+						// move the top up to 0
+						this.max = 0;
+					} else if (minSign > 0 && maxSign > 0) {
+						// move the botttom down to 0
+						this.min = 0;
+					}
 				}
 				
 				var niceRange = helpers.niceNum(this.max - this.min, false);