DataView

Contents

Overview

A DataView offers a filtered and/or formatted view on a DataSet. One can subscribe to changes in a DataView, and easily get filtered or formatted data without having to specify filters and field types all the time.

Example

The following example shows how to use a DataView.

// create a DataSet
var data = new vis.DataSet();
data.add([
  {id: 1, text: 'item 1', date: new Date(2013, 6, 20), group: 1, first: true},
  {id: 2, text: 'item 2', date: '2013-06-23', group: 2},
  {id: 3, text: 'item 3', date: '2013-06-25', group: 2},
  {id: 4, text: 'item 4'}
]);

// create a DataView
// the view will only contain items having a property group with value 1,
// and will only output fields id, text, and date.
var view = new vis.DataView(data, {
  filter: function (item) {
    return (item.group == 1);
  },
  fields: ['id', 'text', 'date']
});

// subscribe to any change in the DataView
view.on('*', function (event, properties, senderId) {
  console.log('event', event, properties);
});

// update an item in the data set
data.update({id: 2, group: 1});

// get all ids in the view
var ids = view.getIds();
console.log('ids', ids); // will output [1, 2]

// get all items in the view
var items = view.get();

Construction

A DataView can be constructed as:

var data = new vis.DataView(dataset, options)

where:

Methods

DataView contains the following methods.

Method Return Type Description
get([options] [, data])
get(id [,options] [, data])
get(ids [, options] [, data])
Object | Array Get a single item, multiple items, or all items from the DataView. Usage examples can be found in section Getting Data, and the available options are described in section Data Selection.
getDataSet() DataSet Get the DataSet to which the DataView is connected.
getIds([options]) Number[] Get ids of all items or of a filtered set of items. Available options are described in section Data Selection, except that options fields and type are not applicable in case of getIds.
off(event, callback) none Unsubscribe from an event, remove an event listener. See section Subscriptions.
on(event, callback) none Subscribe to an event, add an event listener. See section Subscriptions.
refresh() none Refresh the filter results of a DataView. Useful when the filter function contains dynamic properties, like:
var data = new vis.DataSet(...);
var view = new vis.DataView(data, {
  filter: function (item) {
    return item.value > threshold;
  }
});
In this example, threshold is an external parameter. When the value of threshold changes, the DataView must be notified that the filter results may have changed by calling DataView.refresh().
setData(data) none Replace the DataSet of the DataView. Parameter data can be a DataSet or a DataView.

Properties

DataView contains the following properties.

Property Type Description
length Number The number of items in the DataView.

Getting Data

Data of the DataView can be retrieved using the method get.

var items = view.get();

Data of a DataView can be filtered and formatted again, in exactly the same way as in a DataSet. See sections Data Manipulation and Data Selection for more information.

var items = view.get({
  fields: ['id', 'score'],
  filter: function (item) {
    return (item.score > 50);
  }
});

Subscriptions

One can subscribe on changes in the DataView. Subscription works exactly the same as for DataSets. See the documentation on subscriptions in a DataSet for more information.

// create a DataSet and a view on the data set
var data = new vis.DataSet();
var view = new vis.DataView({
  filter: function (item) {
    return (item.group == 2);
  }
});

// subscribe to any change in the DataView
view.on('*', function (event, properties, senderId) {
  console.log('event:', event, 'properties:', properties, 'senderId:', senderId);
});

// add, update, and remove data in the DataSet...