# Logistic
> Logistic distribution constructor.
## Usage
```javascript
var Logistic = require( '@stdlib/stats/base/dists/logistic/ctor' );
```
#### Logistic( \[mu, s] )
Returns a [logistic][logistic-distribution] distribution object.
```javascript
var logistic = new Logistic();
var mu = logistic.mean;
// returns 0.0
```
By default, `mu = 0.0` and `s = 1.0`. To create a distribution having a different `mu` (location parameter) and `s` (scale parameter), provide the corresponding arguments.
```javascript
var logistic = new Logistic( 2.0, 4.0 );
var mu = logistic.mean;
// returns 2.0
```
* * *
## logistic
A [logistic][logistic-distribution] distribution object has the following properties and methods...
### Writable Properties
#### logistic.mu
Location parameter of the distribution.
```javascript
var logistic = new Logistic();
var mu = logistic.mu;
// returns 0.0
logistic.mu = 3.0;
mu = logistic.mu;
// returns 3.0
```
#### logistic.s
Scale parameter of the distribution. `s` **must** be a positive number.
```javascript
var logistic = new Logistic( 2.0, 4.0 );
var s = logistic.s;
// returns 4.0
logistic.s = 3.0;
s = logistic.s;
// returns 3.0
```
* * *
### Computed Properties
#### Logistic.prototype.entropy
Returns the [differential entropy][entropy].
```javascript
var logistic = new Logistic( 4.0, 12.0 );
var entropy = logistic.entropy;
// returns ~4.485
```
#### Logistic.prototype.kurtosis
Returns the [excess kurtosis][kurtosis].
```javascript
var logistic = new Logistic( 4.0, 12.0 );
var kurtosis = logistic.kurtosis;
// returns 1.2
```
#### Logistic.prototype.mean
Returns the [expected value][expected-value].
```javascript
var logistic = new Logistic( 4.0, 12.0 );
var mu = logistic.mean;
// returns 4.0
```
#### Logistic.prototype.median
Returns the [median][median].
```javascript
var logistic = new Logistic( 4.0, 12.0 );
var median = logistic.median;
// returns 4.0
```
#### Logistic.prototype.mode
Returns the [mode][mode].
```javascript
var logistic = new Logistic( 4.0, 12.0 );
var mode = logistic.mode;
// returns 4.0
```
#### Logistic.prototype.skewness
Returns the [skewness][skewness].
```javascript
var logistic = new Logistic( 4.0, 12.0 );
var skewness = logistic.skewness;
// returns 0.0
```
#### Logistic.prototype.stdev
Returns the [standard deviation][standard-deviation].
```javascript
var logistic = new Logistic( 4.0, 12.0 );
var s = logistic.stdev;
// returns ~21.766
```
#### Logistic.prototype.variance
Returns the [variance][variance].
```javascript
var logistic = new Logistic( 4.0, 12.0 );
var s2 = logistic.variance;
// returns ~473.741
```
* * *
### Methods
#### Logistic.prototype.cdf( x )
Evaluates the [cumulative distribution function][cdf] (CDF).
```javascript
var logistic = new Logistic( 2.0, 4.0 );
var y = logistic.cdf( 0.5 );
// returns ~0.407
```
#### Logistic.prototype.logcdf( x )
Evaluates the natural logarithm of the [cumulative distribution function][cdf] (CDF).
```javascript
var logistic = new Logistic( 2.0, 4.0 );
var y = logistic.logcdf( 2.0 );
// returns ~-0.693
```
#### Logistic.prototype.logpdf( x )
Evaluates the natural logarithm of the [probability density function][pdf] (PDF).
```javascript
var logistic = new Logistic( 2.0, 4.0 );
var y = logistic.logpdf( 0.8 );
// returns ~-2.795
```
#### Logistic.prototype.mgf( t )
Evaluates the [moment-generating function][mgf] (MGF).
```javascript
var logistic = new Logistic( 2.0, 4.0 );
var y = logistic.mgf( 0.2 );
// returns ~6.379
```
#### Logistic.prototype.pdf( x )
Evaluates the [probability density function][pdf] (PDF).
```javascript
var logistic = new Logistic( 2.0, 4.0 );
var y = logistic.pdf( 2.0 );
// returns 0.0625
```
#### Logistic.prototype.quantile( p )
Evaluates the [quantile function][quantile-function] at probability `p`.
```javascript
var logistic = new Logistic( 2.0, 4.0 );
var y = logistic.quantile( 0.5 );
// returns 2.0
y = logistic.quantile( 1.9 );
// returns NaN
```
* * *
## Examples
```javascript
var Logistic = require( '@stdlib/stats/base/dists/logistic/ctor' );
var logistic = new Logistic( 2.0, 4.0 );
var mean = logistic.mean;
// returns 2.0
var median = logistic.median;
// returns 2.0
var s2 = logistic.variance;
// returns ~52.638
var y = logistic.cdf( 0.8 );
// returns ~0.426
```
[logistic-distribution]: https://en.wikipedia.org/wiki/Logistic_distribution
[cdf]: https://en.wikipedia.org/wiki/Cumulative_distribution_function
[mgf]: https://en.wikipedia.org/wiki/Moment-generating_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
[expected-value]: https://en.wikipedia.org/wiki/Expected_value
[kurtosis]: https://en.wikipedia.org/wiki/Kurtosis
[median]: https://en.wikipedia.org/wiki/Median
[mode]: https://en.wikipedia.org/wiki/Mode_%28statistics%29
[skewness]: https://en.wikipedia.org/wiki/Skewness
[standard-deviation]: https://en.wikipedia.org/wiki/Standard_deviation
[variance]: https://en.wikipedia.org/wiki/Variance