<!-- @license Apache-2.0 Copyright (c) 2018 The Stdlib Authors. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. --> # Common Logarithm > Evaluate the [common logarithm][common-logarithm]. <section class="intro"> The [common logarithm][common-logarithm] (logarithm with base 10) is defined for any positive real number as <!-- <equation class="equation" label="eq:common_logarithm" align="center" raw="\quad \log_{10} \left( x \right) = y \quad \text{such that} \quad 10^y = x" alt="Equation for the common logarithm."> --> <div class="equation" align="center" data-raw-text="\quad \log_{10} \left( x \right) = y \quad \text{such that} \quad 10^y = x" data-equation="eq:common_logarithm"> <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@8cb4d022f6163be6523964802725ed2a74f2497b/lib/node_modules/@stdlib/math/base/special/log10/docs/img/equation_common_logarithm.svg" alt="Equation for the common logarithm."> <br> </div> <!-- </equation> --> </section> <!-- /.intro --> <section class="usage"> ## Usage ```javascript var log10 = require( '@stdlib/math/base/special/log10' ); ``` #### log10( x ) Evaluates the [common logarithm][common-logarithm]. ```javascript var v = log10( 100.0 ); // returns 2.0 v = log10( 8.0 ); // returns ~0.903 v = log10( 0.0 ); // returns -Infinity v = log10( Infinity ); // returns Infinity v = log10( NaN ); // returns NaN ``` For negative numbers, the [common logarithm][common-logarithm] is **not** defined. ```javascript var v = log10( -4.0 ); // returns NaN ``` </section> <!-- /.usage --> <section class="examples"> ## Examples <!-- eslint no-undef: "error" --> ```javascript var randu = require( '@stdlib/random/base/randu' ); var round = require( '@stdlib/math/base/special/round' ); var log10 = require( '@stdlib/math/base/special/log10' ); var x; var i; for ( i = 0; i < 100; i++ ) { x = round( randu() * 100.0 ); console.log( 'log10(%d) = %d', x, log10( x ) ); } ``` </section> <!-- /.examples --> <section class="links"> [common-logarithm]: https://en.wikipedia.org/wiki/Common_logarithm </section> <!-- /.links -->