99 lines
1.9 KiB
Markdown
99 lines
1.9 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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# log1p
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> Evaluate the [natural logarithm][@stdlib/math/base/special/ln] of `1+x`.
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<section class="usage">
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## Usage
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```javascript
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var log1p = require( '@stdlib/math/base/special/log1p' );
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```
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#### log1p( x )
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Evaluates the [natural logarithm][@stdlib/math/base/special/ln] of `1+x`.
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```javascript
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var v = log1p( 4.0 );
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// returns ~1.609
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v = log1p( -1.0 );
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// returns -Infinity
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v = log1p( Infinity );
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// returns Infinity
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v = log1p( 0.0 );
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// returns 0.0
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v = log1p( -0.0 );
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// returns -0.0
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v = log1p( NaN );
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// returns NaN
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```
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For `x < -1`, the function returns `NaN`, as the [natural logarithm][@stdlib/math/base/special/ln] is **not** defined for negative numbers.
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```javascript
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var v = log1p( -2.0 );
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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 round = require( '@stdlib/math/base/special/round' );
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var log1p = require( '@stdlib/math/base/special/log1p' );
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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 = round( randu() * 100.0 );
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console.log( log1p( 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/ln]: https://www.npmjs.com/package/@stdlib/math/tree/main/base/special/ln
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</section>
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<!-- /.links -->
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