function quantile( r ) {
		if ( isnan( r ) || r < 0.0 || r > 1.0 ) {
			return NaN;
		}
		if ( r === 1.0 ) {
			return PINF;
		}
		return max( 0.0, ceil( ( ln(1.0-r)/log1p(-p) ) - ( 1.0+1.0e-12 ) ) );
	}
Evaluates the quantile function for a geometric distribution.

@private
@param {Probability} r - input value
@returns {NonNegativeInteger} evaluated quantile function

@example
var y = quantile( 0.3 );
// returns <number>