Bar graph added.

node_modules/vega-view/src/data.js

@@ -0,0 +1,33 @@
+import {changeset, isChangeSet} from 'vega-dataflow';
+import {error, hasOwnProperty, truthy} from 'vega-util';
+
+export function dataref(view, name) {
+  var data = view._runtime.data;
+  if (!hasOwnProperty(data, name)) {
+    error('Unrecognized data set: ' + name);
+  }
+  return data[name];
+}
+
+export function data(name, values) {
+  return arguments.length < 2
+    ? dataref(this, name).values.value
+    : change.call(this, name, changeset().remove(truthy).insert(values));
+}
+
+export function change(name, changes) {
+  if (!isChangeSet(changes)) {
+    error('Second argument to changes must be a changeset.');
+  }
+  var dataset = dataref(this, name);
+  dataset.modified = true;
+  return this.pulse(dataset.input, changes);
+}
+
+export function insert(name, _) {
+  return change.call(this, name, changeset().insert(_));
+}
+
+export function remove(name, _) {
+  return change.call(this, name, changeset().remove(_));
+}