85 lines
1.6 KiB
Markdown
85 lines
1.6 KiB
Markdown
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<!--
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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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# gamma1pm1
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> Compute `gamma(x+1) - 1`.
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<section class="usage">
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## Usage
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```javascript
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var gamma1pm1 = require( '@stdlib/math/base/special/gamma1pm1' );
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```
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#### gamma1pm1( x )
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Computes `gamma(x+1) - 1` without cancellation errors for small `x` and where `gamma(x)` is the [gamma function][@stdlib/math/base/special/gamma].
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```javascript
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var v = gamma1pm1( 0.2 );
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// returns ~-0.082
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v = gamma1pm1( -8.5 );
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// returns ~-1.0
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v = gamma1pm1( 0.0 );
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// returns 0.0
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v = gamma1pm1( NaN );
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// returns NaN
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```
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</section>
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<!-- /.usage -->
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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 gamma1pm1 = require( '@stdlib/math/base/special/gamma1pm1' );
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var x;
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var i;
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for ( i = 0; i < 100; i++ ) {
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x = (randu()*10.0) - 5.0;
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console.log( 'gamma(%d+1) - 1 = %d', x, gamma1pm1( x ) );
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}
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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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[@stdlib/math/base/special/gamma]: https://www.npmjs.com/package/@stdlib/math/tree/main/base/special/gamma
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</section>
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<!-- /.links -->
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