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# 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 discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var logEachMap = require( '@stdlib/console/log-each-map' );
var log10 = require( '@stdlib/math/base/special/log10' );

var opts = {
    'dtype': 'float64'
};
var x = discreteUniform( 100, 0, 100, opts );

logEachMap( 'log10(%d) = %0.4f', x, log10 );
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/math/base/special/log10.h"
```

#### stdlib_base_log10( x )

Evaluates the [common logarithm][common-logarithm].

```c
double out = stdlib_base_log10( 100.0 );
// returns 2.0

out = stdlib_base_log10( 8.0 );
// returns ~0.903
```

The function accepts the following arguments:

-   **x**: `[in] double` input value.

```c
double stdlib_base_log10( const double x );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/math/base/special/log10.h"
#include <stdlib.h>
#include <stdio.h>

int main( void ) {
    double x;
    double v;
    int i;

    for ( i = 0; i < 100; i++ ) {
        x = ( (double)rand() / (double)RAND_MAX ) * 100.0;
        v = stdlib_base_log10( x );
        printf( "log10(%lf) = %lf\n", x, v );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/math/base/special/exp10`][@stdlib/math/base/special/exp10]</span><span class="delimiter">: </span><span class="description">base 10 exponential function.</span>
-   <span class="package-name">[`@stdlib/math/base/special/ln`][@stdlib/math/base/special/ln]</span><span class="delimiter">: </span><span class="description">evaluate the natural logarithm of a double-precision floating-point number.</span>
-   <span class="package-name">[`@stdlib/math/base/special/log`][@stdlib/math/base/special/log]</span><span class="delimiter">: </span><span class="description">compute the base `b` logarithm of a double-precision floating-point number.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

[common-logarithm]: https://en.wikipedia.org/wiki/Common_logarithm

<!-- <related-links> -->

[@stdlib/math/base/special/exp10]: https://github.com/stdlib-js/math/tree/main/base/special/exp10

[@stdlib/math/base/special/ln]: https://github.com/stdlib-js/math/tree/main/base/special/ln

[@stdlib/math/base/special/log]: https://github.com/stdlib-js/math/tree/main/base/special/log

<!-- </related-links> -->

</section>

<!-- /.links -->
