## Usage ```javascript var incrmmeanabs2 = require( '@stdlib/stats/incr/mmeanabs2' ); ``` #### incrmmeanabs2( window ) Returns an accumulator `function` which incrementally computes a moving [arithmetic mean][arithmetic-mean] of squared absolute values. The `window` parameter defines the number of values over which to compute the moving mean. ```javascript var accumulator = incrmmeanabs2( 3 ); ``` #### accumulator( \[x] ) If provided an input value `x`, the accumulator function returns an updated mean. If not provided an input value `x`, the accumulator function returns the current mean. ```javascript var accumulator = incrmmeanabs2( 3 ); var m = accumulator(); // returns null // Fill the window... m = accumulator( 2.0 ); // [2.0] // returns 4.0 m = accumulator( -1.0 ); // [2.0, -1.0] // returns 2.5 m = accumulator( 3.0 ); // [2.0, -1.0, 3.0] // returns ~4.67 // Window begins sliding... m = accumulator( -7.0 ); // [-1.0, 3.0, -7.0] // returns ~19.67 m = accumulator( -5.0 ); // [3.0, -7.0, -5.0] // returns ~27.67 m = accumulator(); // returns ~27.67 ```

## Notes - Input values are **not** type checked. If provided `NaN` or a value which, when used in computations, results in `NaN`, the accumulated value is `NaN` for **at least** `W-1` future invocations. If non-numeric inputs are possible, you are advised to type check and handle accordingly **before** passing the value to the accumulator function. - As `W` values are needed to fill the window buffer, the first `W-1` returned values are calculated from smaller sample sizes. Until the window is full, each returned value is calculated from all provided values.

## Examples ```javascript var randu = require( '@stdlib/random/base/randu' ); var incrmmeanabs2 = require( '@stdlib/stats/incr/mmeanabs2' ); var accumulator; var v; var i; // Initialize an accumulator: accumulator = incrmmeanabs2( 5 ); // For each simulated datum, update the moving mean... for ( i = 0; i < 100; i++ ) { v = ( randu()*100.0 ) - 50.0; accumulator( v ); } console.log( accumulator() ); ```