function lognormal2( mu, sigma ) {
		if (
			isnan( mu ) ||
			isnan( sigma ) ||
			sigma <= 0.0
		) {
			return NaN;
		}
		return lognormal0( rnorm, mu, sigma );
	}
Returns a log-normally distributed pseudorandom number with parameters `mu` and `sigma`.

@private
@param {number} mu - location parameter
@param {PositiveNumber} sigma - scale parameter
@returns {PositiveNumber} pseudorandom number

@example
var v = lognormal2( -2.0, 4.0 );
// returns <number>

@example
var v = lognormal2( 0.0, -1.0 );
// returns NaN