function quantile( p, k, lambda ) {
	if ( !isNonNegativeInteger( k ) ) {
		return NaN;
	}
	return quantileGamma( p, k, lambda );
}
Evaluates the quantile function for an Erlang distribution with shape parameter `k` and rate parameter `lambda` at a probability `p`.

@param {Probability} p - input value
@param {NonNegativeInteger} k - shape parameter
@param {PositiveNumber} lambda - rate parameter
@returns {number} evaluated quantile function

@example
var y = quantile( 0.8, 2, 1.0 );
// returns ~2.994

@example
var y = quantile( 0.5, 4, 2.0 );
// returns ~1.836

@example
var y = quantile( 1.1, 1, 1.0 );
// returns NaN

@example
var y = quantile( -0.2, 1, 1.0 );
// returns NaN

@example
var y = quantile( NaN, 1, 1.0 );
// returns NaN

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

@example
var y = quantile( 0.0, 1, NaN );
// returns NaN

@example
// Non-integer shape parameter:
var y = quantile( 0.5, 0.5, 1.0 );
// returns NaN

@example
// Non-positive shape parameter:
var y = quantile( 0.5, -1, 1.0 );
// returns NaN

@example
// Non-positive rate parameter:
var y = quantile( 0.5, 1, -1.0 );
// returns NaN