95 lines
1.7 KiB
Markdown
95 lines
1.7 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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# Logarithm
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> Compute the base `b` [logarithm][logarithm].
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<section class="usage">
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## Usage
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```javascript
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var log = require( '@stdlib/math/base/special/log' );
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```
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#### log( x, b )
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Computes the base `b` logarithm of `x`.
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```javascript
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var v = log( 100.0, 10.0 );
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// returns 2.0
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v = log( 16.0, 2.0 );
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// returns 4.0
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v = log( 5.0, 1.0 );
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// returns Infinity
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```
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For negative `x` or `b`, the [logarithm][logarithm] is **not** defined.
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```javascript
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var v = log( -4.0, 1.0 );
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// returns NaN
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v = log( 2.0, -4.0 );
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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 log = require( '@stdlib/math/base/special/log' );
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var b;
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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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b = round( randu() * 5.0 );
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console.log( 'log( %d, %d ) = %d', x, b, log( x, b ) );
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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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[logarithm]: https://en.wikipedia.org/wiki/Logarithm
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</section>
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<!-- /.links -->
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