@stdlib/stats/base/dists/cauchy/ctor/README.md

Standard library statistical functions.

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# Cauchy

> Cauchy distribution constructor.

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## Usage

```javascript
var Cauchy = require( '@stdlib/stats/base/dists/cauchy/ctor' );
```

#### Cauchy( \[x0, gamma] )

Returns a [Cauchy][cauchy-distribution] distribution object.

```javascript
var cauchy = new Cauchy();

var median = cauchy.median;
// returns 0.0
```

By default, `x0 = 0.0` and `gamma = 1.0`. To create a distribution having a different `x0` (location parameter) and `gamma` (scale parameter), provide the corresponding arguments.

```javascript
var cauchy = new Cauchy( 2.0, 4.0 );

var median = cauchy.median;
// returns 2.0
```

* * *

## cauchy

A [Cauchy][cauchy-distribution] distribution object has the following properties and methods...

### Writable Properties

#### cauchy.x0

Location parameter of the distribution.

```javascript
var cauchy = new Cauchy();

var x0 = cauchy.x0;
// returns 0.0

cauchy.x0 = 3.0;

x0 = cauchy.x0;
// returns 3.0
```

#### cauchy.gamma

Scale parameter of the distribution. `gamma` **must** be a positive number.

```javascript
var cauchy = new Cauchy( 2.0, 4.0 );

var gamma = cauchy.gamma;
// returns 4.0

cauchy.gamma = 3.0;

gamma = cauchy.gamma;
// returns 3.0
```

* * *

### Computed Properties

#### Cauchy.prototype.entropy

Returns the [differential entropy][entropy].

```javascript
var cauchy = new Cauchy( 4.0, 12.0 );

var entropy = cauchy.entropy;
// returns ~5.016
```

#### Cauchy.prototype.median

Returns the [median][median].

```javascript
var cauchy = new Cauchy( 4.0, 12.0 );

var median = cauchy.median;
// returns 4.0
```

#### Cauchy.prototype.mode

Returns the [mode][mode].

```javascript
var cauchy = new Cauchy( 4.0, 12.0 );

var mode = cauchy.mode;
// returns 4.0
```

* * *

### Methods

#### Cauchy.prototype.cdf( x )

Evaluates the [cumulative distribution function][cdf] (CDF).

```javascript
var cauchy = new Cauchy( 2.0, 4.0 );

var y = cauchy.cdf( 0.5 );
// returns ~0.386
```

#### Cauchy.prototype.logcdf( x )

Evaluates the natural logarithm of the [cumulative distribution function][cdf] (CDF).

```javascript
var cauchy = new Cauchy( 2.0, 4.0 );

var y = cauchy.logcdf( 0.5 );
// returns ~-0.952
```

#### Cauchy.prototype.logpdf( x )

Evaluates the natural logarithm of the [probability density function][pdf] (PDF).

```javascript
var cauchy = new Cauchy( 2.0, 4.0 );

var y = cauchy.logpdf( 0.8 );
// returns ~-2.617
```

#### Cauchy.prototype.pdf( x )

Evaluates the [probability density function][pdf] (PDF).

```javascript
var cauchy = new Cauchy( 2.0, 4.0 );

var y = cauchy.pdf( 0.8 );
// returns ~0.073
```

#### Cauchy.prototype.quantile( p )

Evaluates the [quantile function][quantile-function] at probability `p`.

```javascript
var cauchy = new Cauchy( 2.0, 4.0 );

var y = cauchy.quantile( 0.5 );
// returns 2.0

y = cauchy.quantile( 1.9 );
// returns NaN
```

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* * *

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## Examples

<!-- eslint no-undef: "error" -->

```javascript
var Cauchy = require( '@stdlib/stats/base/dists/cauchy/ctor' );

var cauchy = new Cauchy( 2.0, 4.0 );

var entropy = cauchy.entropy;
// returns ~3.917

var median = cauchy.median;
// returns 2.0

var mode = cauchy.mode;
// returns 2.0

var y = cauchy.cdf( 0.8 );
// returns ~0.407
```

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[cauchy-distribution]: https://en.wikipedia.org/wiki/Cauchy_distribution

[cdf]: https://en.wikipedia.org/wiki/Cumulative_distribution_function

[pdf]: https://en.wikipedia.org/wiki/Probability_density_function

[quantile-function]: https://en.wikipedia.org/wiki/Quantile_function

[entropy]: https://en.wikipedia.org/wiki/Entropy_%28information_theory%29

[median]: https://en.wikipedia.org/wiki/Median

[mode]: https://en.wikipedia.org/wiki/Mode_%28statistics%29

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