function factory( mu, s ) {
	if ( isnan( mu ) || isnan( s ) || s < 0.0 ) {
		return constantFunction( NaN );
	}
	if ( s === 0.0 ) {
		return degenerate( mu );
	}
	return mgf;

	/**
	* Evaluates the moment-generating function (MGF) for a logistic distribution.
	*
	* @private
	* @param {number} t - input value
	* @returns {number} evaluated MGF
	*
	* @example
	* var y = mgf( 0.5 );
	* // returns <number>
	*/
	function mgf( t ) {
		var st = s * t;
		if ( abs( st ) > 1.0 ) {
			return NaN;
		}
		return exp( mu * t ) / sinc( st );
	}
}
Returns a function for evaluating the moment-generating function (MGF) of a logistic distribution with mean `mu` and scale parameter `s`.

@param {number} mu - mean
@param {NonNegativeNumber} s - scale parameter
@returns {Function} MGF

@example
var mgf = factory( 10.0, 0.5 );

var y = mgf( 0.5 );
// returns ~164.846

y = mgf( 2.0 );
// returns Infinity