Build the lookup map for initialized categories

Author: hy9be

src/plots/plots.js

@@ -1950,6 +1950,13 @@ plots.doCalcdata = function(gd, traces) {
     // to be filled in later by ax.d2c
     for(i = 0; i < axList.length; i++) {
         axList[i]._categories = axList[i]._initialCategories.slice();
+
+        //Build the lookup map for initialized categories
+        axList[i]._categoriesMap = {};
+        for (var j = 0; j < axList[i]._categories.length; j++) {
+            axList[i]._categoriesMap[axList[i]._categories[j]] = j;
+        }
+
         if(axList[i].type === 'category') hasCategoryAxis = true;
     }