Improve findMinMax for stacked charts

src/axis.js

@@ -396,6 +396,11 @@ c3_chart_internal_fn.tuneAxis = function(sync, callback){
             sizesX = $$.getAbscissa($$.config.ed3Type, minmax.minX, minmax.maxX);
         }
         var sizesY = $$.getAxisData(minmax.minY, minmax.maxY);
+        
+        if($$.config.normalized){
+            sizesY.max = Math.min(sizesY.max, 1);
+            sizesY.min = Math.max(sizesY.min, -1);
+        }
 
         $$.api.axis.range({
             min: {
@@ -423,7 +428,10 @@ c3_chart_internal_fn.tuneAxis = function(sync, callback){
 
 c3_chart_internal_fn.findMinMax = function () {
     var $$ = this;
-    var minY, maxY, minX, maxX;
+    var minY = Infinity,
+        maxY = -Infinity,
+        minX = Infinity,
+        maxX = -Infinity;
     var i,j, id;
 
     var stacked;
@@ -440,6 +448,11 @@ c3_chart_internal_fn.findMinMax = function () {
         });
     }
     
+    // For stacked bar(different algorithm)
+    var stackedBarSumUp = [];
+    var stackedBarSumDown = [];
+    
+    // For all other charts
     var stackedSum = [];
 
     var allData = $$.api.data();
@@ -450,33 +463,45 @@ c3_chart_internal_fn.findMinMax = function () {
 
         // calc min/max for X axis
         for(i = 0; i < data.length; i++) {
-            if (isUndefined(maxX) || data[i].x > maxX)
-                maxX = data[i].x;
-            if (isUndefined(minX) || data[i].x < minX)
-                minX = data[i].x;
+            minX = Math.min(minX, data[i].x);
+            maxX = Math.max(maxX, data[i].x);
         }
 
         // calc min/max for Y axis
         for(i = 0; i < data.length; i++) {
-            if (isUndefined(maxY) || data[i].value > maxY)
-                maxY = data[i].value;
-            if (isUndefined(minY) || data[i].value < minY)
-                minY = data[i].value;
             // calc sum row for stacked
             if (stacked) {
-                if (!stackedSum[i])
+                if (stackedSum[i] === undefined){
                     stackedSum[i] = 0;
-                stackedSum[i] += data[i].value;
+                    stackedBarSumUp[i] = 0;
+                    stackedBarSumDown[i] = 0;
+                }
+                // Stacked algorithm differs for bar and other charts
+                if ($$.isBarType(v)){
+                    stackedBarSumUp[i] += Math.max(0, data[i].value);
+                    stackedBarSumDown[i] += Math.min(0, data[i].value);
+                } else {
+                    stackedSum[i] += data[i].value;
+                    minY = Math.min(minY, stackedSum[i]);
+                    maxY = Math.max(maxY, stackedSum[i]);
+                }
+            } else {
+                minY = Math.min(minY, data[i].value);
+                maxY = Math.max(maxY, data[i].value);
             }
         }
     });
 
     if (stacked) {
         for(i = 0; i < stackedSum.length; i++) {
-            if (isUndefined(maxY) || stackedSum[i] > maxY)
-                maxY = stackedSum[i];
-            if (isUndefined(minY) || stackedSum[i] < minY)
-                minY = stackedSum[i];
+            minY = Math.min(
+                minY, stackedSum[i],
+                stackedBarSumDown[i], stackedBarSumUp[i]
+            );
+            maxY = Math.max(
+                maxY, stackedSum[i],
+                stackedBarSumDown[i], stackedBarSumUp[i]
+            );
         }
     }