121 lines
2.9 KiB
Markdown
121 lines
2.9 KiB
Markdown
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# incrmmaxabs
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> Compute a moving maximum absolute value incrementally.
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<section class="usage">
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## Usage
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```javascript
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var incrmmaxabs = require( '@stdlib/stats/incr/mmaxabs' );
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```
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#### incrmmaxabs( window )
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Returns an accumulator `function` which incrementally computes a moving maximum absolute value. The `window` parameter defines the number of values over which to compute the moving maximum absolute value.
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```javascript
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var accumulator = incrmmaxabs( 3 );
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```
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#### accumulator( \[x] )
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If provided an input value `x`, the accumulator function returns an updated maximum absolute value. If not provided an input value `x`, the accumulator function returns the current maximum absolute value.
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```javascript
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var accumulator = incrmmaxabs( 3 );
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var m = accumulator();
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// returns null
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// Fill the window...
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m = accumulator( 2.0 ); // [2.0]
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// returns 2.0
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m = accumulator( 1.0 ); // [2.0, 1.0]
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// returns 2.0
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m = accumulator( 3.0 ); // [2.0, 1.0, 3.0]
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// returns 3.0
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// Window begins sliding...
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m = accumulator( -7.0 ); // [1.0, 3.0, -7.0]
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// returns 7.0
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m = accumulator( -5.0 ); // [3.0, -7.0, -5.0]
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// returns 7.0
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m = accumulator();
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// returns 7.0
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- Input values are **not** type checked. If provided `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.
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- 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.
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var randu = require( '@stdlib/random/base/randu' );
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var incrmmaxabs = require( '@stdlib/stats/incr/mmaxabs' );
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var accumulator;
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var v;
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var i;
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// Initialize an accumulator:
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accumulator = incrmmaxabs( 5 );
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// For each simulated datum, update the moving maximum absolute value...
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for ( i = 0; i < 100; i++ ) {
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v = ( randu()*100.0 ) - 50.0;
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accumulator( v );
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}
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console.log( accumulator() );
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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</section>
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<!-- /.links -->
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