function cdf( x, mu, sigma ) {
	if (
		isnan( x ) ||
		isnan( mu ) ||
		isnan( sigma ) ||
		sigma <= 0.0
	) {
		return NaN;
	}
	if ( x <= 0.0 ) {
		return 0.0;
	}
	return normalCDF( ln(x), mu, sigma );
}
Evaluates the cumulative distribution function (CDF) for a lognormal distribution with location parameter `mu` and scale parameter `sigma` at a value `x`.

@param {number} x - input value
@param {number} mu - location parameter
@param {PositiveNumber} sigma - scale parameter
@returns {Probability} evaluated CDF

@example
var y = cdf( 2.0, 0.0, 1.0 );
// returns ~0.756

@example
var y = cdf( 5.0, 10.0, 3.0 );
// returns ~0.003

@example
var y = cdf( 2.0, 0.0, NaN );
// returns NaN

@example
var y = cdf( 2.0, NaN, 1.0 );
// returns NaN

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