function boxcox1pinv( y, lambda ) {
	var ly;
	if ( isnan( y ) || isnan( lambda ) ) {
		return NaN;
	}
	if ( lambda === 0.0 ) {
		return expm1( y );
	}
	ly = lambda * y;
	if ( abs( ly ) < 1.0e-154 ) {
		return y;
	}
	return expm1( log1p( ly ) / lambda );
}
Computes the inverse of a one-parameter Box-Cox transformation for `1+x`.

@param {number} y - input value
@param {number} lambda - power parameter
@returns {number} inverse of the Box-Cox transformation

@example
var v = boxcox1pinv( 1.0, 2.5 );
// returns ~0.6505

@example
var v = boxcox1pinv( 4.0, 2.5 );
// returns ~1.6095

@example
var v = boxcox1pinv( 10.0, 2.5 );
// returns ~2.6812

@example
var v = boxcox1pinv( 2.0, 0.0 );
// returns ~6.3891

@example
var v = boxcox1pinv( -1.0, 2.5 );
// returns NaN

@example
var v = boxcox1pinv( 0.0, -1.0 );
// returns 0.0

@example
var v = boxcox1pinv( 1.0, NaN );
// returns NaN

@example
var v = boxcox1pinv( NaN, 3.1 );
// returns NaN