# Quantile Function

Raised cosine distribution quantile function.

## Usage

``````var quantile = require( '@stdlib/math/base/dists/cosine/quantile' );
``````

#### quantile( p, mu, s )

Evaluates the quantile function for a raised cosine distribution with parameters `mu` (location parameter) and `s` (scale parameter).

``````var y = quantile( 0.5, 0.0, 1.0 );
// returns 0.0

y = quantile( 0.2, 4.0, 2.0 );
// returns ~3.345
``````

If provided a probability `p` outside the interval `[0,1]`, the function returns `NaN`.

``````var y = quantile( 1.9, 0.0, 1.0 );
// returns NaN

y = quantile( -0.1, 0.0, 1.0 );
// returns NaN
``````

If provided `NaN` as any argument, the function returns `NaN`.

``````var y = quantile( NaN, 0.0, 1.0 );
// returns NaN

y = quantile( 0.0, NaN, 1.0 );
// returns NaN

y = quantile( 0.0, 0.0, NaN );
// returns NaN
``````

If provided `s < 0`, the function returns `NaN`.

``````var y = quantile( 0.4, 0.0, -1.0 );
// returns NaN
``````

If provided `s = 0`, the function evaluates the quantile function of a degenerate distribution centered at `mu`.

``````var y = quantile( 0.3, 8.0, 0.0 );
// returns 8.0

y = quantile( 0.9, 8.0, 0.0 );
// returns 8.0
``````

#### quantile.factory( mu, s )

Returns a function for evaluating the quantile function of a raised cosine distribution with parameters `mu` and `s`.

``````var myQuantile = quantile.factory( 10.0, 2.0 );

var y = myQuantile( 0.2 );
// returns ~9.345

y = myQuantile( 0.9 );
// returns ~10.964
``````

## Examples

``````var randu = require( '@stdlib/random/base/randu' );
var quantile = require( '@stdlib/math/base/dists/cosine/quantile' );

var mu;
var s;
var p;
var y;
var i;

for ( i = 0; i < 10; i++ ) {
p = randu();
mu = randu() * 10.0;
s = randu() * 10.0;
y = quantile( p, mu, s );
console.log( 'p: %d, µ: %d, s: %d, Q(p;µ,s): %d', p, mu, s, y );
}
``````