function factory( d1, d2 ) {
	if (
		isnan( d1 ) ||
		isnan( d2 ) ||
		d1 <= 0.0 ||
		d2 <= 0.0
	) {
		return constantFunction( NaN );
	}
	return quantile;

	/**
	* Evaluates the quantile function for an F distribution.
	*
	* @private
	* @param {Probability} p - input value
	* @returns {number} evaluated quantile function
	*
	* @example
	* var y = quantile( 0.3 );
	* // returns <number>
	*/
	function quantile( p ) {
		var xs;
		if ( isnan( p ) || p < 0.0 || p > 1.0 ) {
			return NaN;
		}
		xs = kernelBetaincinv( d1/2.0, d2/2.0, p, 1.0 - p );
		return d2 * xs[ 0 ] / ( d1 * xs[ 1 ] );
	}
}
Returns a function for evaluating the quantile function for an F distribution with numerator degrees of freedom `d1` and denominator degrees of freedom `d2`.

@param {PositiveNumber} d1 - numerator degrees of freedom
@param {PositiveNumber} d2 - denominator degrees of freedom
@returns {Function} quantile function

@example
var quantile = factory( 10.0, 2.0 );
var y = quantile( 0.4 );
// returns ~0.994

y = quantile( 0.8 );
// returns ~4.382