doc/api/core/operators/average.md
# This is RxJS v 4. [Find the latest version here](https://github.com/reactivex/rxjs)### `Rx.Observable.prototype.average([selector], [thisArg])`[Ⓢ](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/average.js "View in source") Computes the average of an observable sequence of values that are in the sequence or obtained by invoking a transform function on each element of the input sequence if present. #### Arguments1. `[selector]` *(`Function`)*: A transform function to apply to each element.2. `[thisArg]` *(`Any`)*: Object to use as `this` when executing `selector`. #### Returns*(`Observable`)*: An observable sequence containing a single element with the average of the sequence of values. #### Example```js// Without a selectorvar source = Rx.Observable.range(0, 9).average(); var subscription = source.subscribe( function (x) { console.log('Next: ' + x); }, function (err) { console.log('Error: ' + err); }, function () { console.log('Completed'); }); // => Next: 4// => Completed // With a selectorvar arr = [ { value: 1 }, { value: 2 }, { value: 3 }]; var source = Rx.Observable.from(arr).average(function (x) { return x.value;}); var subscription = source.subscribe( function (x) { console.log('Next: ' + x); }, function (err) { console.log('Error: ' + err); }, function () { console.log('Completed'); }); // => Next: 2// => Completed``` ### Location File:- [`/src/core/linq/observable/average.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/src/core/linq/observable/average.js) Dist:- [`rx.all.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.all.js)- [`rx.all.compat.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.all.js)- [`rx.aggregates.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.aggregates.js) Prerequisites:- [`rx.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.js) | [`rx.compat.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.compat.js) | [`rx.lite.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.lite.js) | [`rx.lite.compat.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/dist/rx.lite.compat.js) NPM Packages:- [`rx`](https://www.npmjs.org/package/rx) NuGet Packages:- [`RxJS-All`](http://www.nuget.org/packages/RxJS-All/)- [`RxJS-Aggregates`](http://www.nuget.org/packages/RxJS-Aggregates/) Unit Tests:- [`/tests/observable/average.js`](https://github.com/Reactive-Extensions/RxJS/blob/master/tests/observable/average.js)