Add appendToColumn function

spec/api.load-spec.js

@@ -118,4 +118,31 @@ describe('c3 api load', function () {
 
     });
 
+    describe('appendToColumn', function(){
+        it('should append values to existing column', function(done){
+            chart.loadColumns([['data1', 0, 100, 200]]);
+            chart.appendToColumn(['data1', 300, 400, 500]);
+
+            var data = chart.getDataById('data1');
+
+            for(var i = 0; i < data.length; i++){
+                expect(data[i].value).toBe(i*100);
+            }
+
+            done();
+        });
+
+        it('should append values to non-existing column', function(done){
+            chart.appendToColumn(['data5', 0, 100, 200, 300]);
+
+            var data = chart.getDataById('data5');
+
+            for(var i = 0; i < data.length; i++){
+                expect(data[i].value).toBe(i*100);
+            }
+
+            done();
+        });
+    });
+
 });

src/api.data.js

@@ -25,3 +25,12 @@ c3_chart_fn.data.colors = function (colors) {
 c3_chart_fn.data.axes = function (axes) {
     return this.internal.updateDataAttributes('axes', axes);
 };
+
+c3_chart_fn.getDataById = function(seqId){
+    var $$ = this.internal;
+    var t = $$.api.data(seqId)[0];
+    if(isUndefined(t)) {
+        return undefined;
+    }
+    return t.values;
+}

src/api.load.js

@@ -55,3 +55,24 @@ c3_chart_fn.unload = function (args) {
         if (args.done) { args.done(); }
     });
 };
+
+c3_chart_fn.appendToColumn = function(col) {
+    var $$ = this.internal;
+    var column = $$.api.getDataById(col[0]);
+
+    if(!isUndefined(column)){
+        for(var i = column.length - 1; i > -1; i--){
+                col.splice(1, 0, column[i].value)
+        }
+    }
+
+    $$.api.loadColumns([col]);
+};
+
+c3_chart_fn.loadColumns = function(cols){
+    var $$ = this.internal;
+    $$.api.load({
+        columns: cols
+    });
+};
+