function mgf( t ) {
		var et;
		var q;
		if ( isnan( t ) ) {
			return NaN;
		}
		q = 1.0 - p;
		if ( t >= -ln( q ) ) {
			return NaN;
		}
		et = exp( t );
		return ( p * et ) / ( 1.0 - (q * et ));
	}
Evaluates the moment-generating function (MGF) for a geometric distribution.

@private
@param {number} t - input value
@returns {number} evaluated MGF

@example
var y = mgf( 0.5 );
// returns <number>