README.md (1748B)
1 <!-- 2 3 @license Apache-2.0 4 5 Copyright (c) 2018 The Stdlib Authors. 6 7 Licensed under the Apache License, Version 2.0 (the "License"); 8 you may not use this file except in compliance with the License. 9 You may obtain a copy of the License at 10 11 http://www.apache.org/licenses/LICENSE-2.0 12 13 Unless required by applicable law or agreed to in writing, software 14 distributed under the License is distributed on an "AS IS" BASIS, 15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 See the License for the specific language governing permissions and 17 limitations under the License. 18 19 --> 20 21 # Logarithm 22 23 > Compute the base `b` [logarithm][logarithm]. 24 25 <section class="usage"> 26 27 ## Usage 28 29 ```javascript 30 var log = require( '@stdlib/math/base/special/log' ); 31 ``` 32 33 #### log( x, b ) 34 35 Computes the base `b` logarithm of `x`. 36 37 ```javascript 38 var v = log( 100.0, 10.0 ); 39 // returns 2.0 40 41 v = log( 16.0, 2.0 ); 42 // returns 4.0 43 44 v = log( 5.0, 1.0 ); 45 // returns Infinity 46 ``` 47 48 For negative `x` or `b`, the [logarithm][logarithm] is **not** defined. 49 50 ```javascript 51 var v = log( -4.0, 1.0 ); 52 // returns NaN 53 54 v = log( 2.0, -4.0 ); 55 // returns NaN 56 ``` 57 58 </section> 59 60 <!-- /.usage --> 61 62 <section class="examples"> 63 64 ## Examples 65 66 <!-- eslint no-undef: "error" --> 67 68 ```javascript 69 var randu = require( '@stdlib/random/base/randu' ); 70 var round = require( '@stdlib/math/base/special/round' ); 71 var log = require( '@stdlib/math/base/special/log' ); 72 73 var b; 74 var x; 75 var i; 76 77 for ( i = 0; i < 100; i++ ) { 78 x = round( randu() * 100.0 ); 79 b = round( randu() * 5.0 ); 80 console.log( 'log( %d, %d ) = %d', x, b, log( x, b ) ); 81 } 82 ``` 83 84 </section> 85 86 <!-- /.examples --> 87 88 <section class="links"> 89 90 [logarithm]: https://en.wikipedia.org/wiki/Logarithm 91 92 </section> 93 94 <!-- /.links -->