Pie doughnut dataset weight

docs/charts/doughnut.md

@@ -62,6 +62,7 @@ The doughnut/pie chart allows a number of properties to be specified for each da
 | `hoverBackgroundColor` | `Color/Color[]` | The fill colour of the arcs when hovered.
 | `hoverBorderColor` | `Color/Color[]` | The stroke colour of the arcs when hovered.
 | `hoverBorderWidth` | `Number/Number[]` | The stroke width of the arcs when hovered.
+| `weight` | `Number` | The relative thickness of the dataset. The default weight of each dataset is 1. Providing a value for weight will allow the pie or doughnut dataset to be drawn with a thickness relative to the sum of all the dataset weights.
 
 ### Border Alignment
 

src/controllers/controller.doughnut.js

@@ -138,6 +138,37 @@ module.exports = DatasetController.extend({
 		return ringIndex;
 	},
 
+	// Get radius length offset of the dataset in relation to the visible datasets weights. This allows determining the inner and outer radius correctly
+	getRingWeightedOffset: function(datasetIndex) {
+		var ringWeightOffset = 0;
+
+		for (var j = 0; j < datasetIndex; ++j) {
+			if (this.chart.isDatasetVisible(j)) {
+				ringWeightOffset += this.getRingWeight(j);
+			}
+		}
+
+		return ringWeightOffset;
+	},
+
+	getRingWeight: function(dataSetIndex) {
+		var ringWeight = this.chart.data.datasets[dataSetIndex].weight;
+		if (!ringWeight) {
+			ringWeight = 1;
+		}
+		return ringWeight;
+	},
+
+	getVisibleDatasetTotalWeight: function() {
+		var totalWeight = 0;
+		for (var i = 0, ilen = this.chart.data.datasets.length; i < ilen; ++i) {
+			if (this.chart.isDatasetVisible(i)) {
+				totalWeight += this.getRingWeight(i);
+			}
+		}
+		return totalWeight;
+	},
+
 	update: function(reset) {
 		var me = this;
 		var chart = me.chart;
@@ -151,6 +182,7 @@ module.exports = DatasetController.extend({
 		var arcs = meta.data;
 		var cutoutPercentage = opts.cutoutPercentage;
 		var circumference = opts.circumference;
+		var chartWeight = chart.data.datasets[me.index].weight ? chart.data.datasets[me.index].weight : 1;
 		var i, ilen;
 
 		// If the chart's circumference isn't a full circle, calculate minSize as a ratio of the width/height of the arc
@@ -179,14 +211,14 @@ module.exports = DatasetController.extend({
 		chart.borderWidth = me.getMaxBorderWidth();
 		chart.outerRadius = Math.max((minSize - chart.borderWidth) / 2, 0);
 		chart.innerRadius = Math.max(cutoutPercentage ? (chart.outerRadius / 100) * (cutoutPercentage) : 0, 0);
-		chart.radiusLength = (chart.outerRadius - chart.innerRadius) / chart.getVisibleDatasetCount();
+		chart.radiusLength = (chart.outerRadius - chart.innerRadius) / me.getVisibleDatasetTotalWeight();
 		chart.offsetX = offset.x * chart.outerRadius;
 		chart.offsetY = offset.y * chart.outerRadius;
 
 		meta.total = me.calculateTotal();
 
-		me.outerRadius = chart.outerRadius - (chart.radiusLength * me.getRingIndex(me.index));
-		me.innerRadius = Math.max(me.outerRadius - chart.radiusLength, 0);
+		me.outerRadius = chart.outerRadius - (chart.radiusLength * me.getRingWeightedOffset(me.index));
+		me.innerRadius = Math.max(me.outerRadius - (chart.radiusLength * chartWeight), 0);
 
 		for (i = 0, ilen = arcs.length; i < ilen; ++i) {
 			me.updateElement(arcs[i], i, reset);