function get() {
	/* eslint-disable no-invalid-this */
	var min;
	if ( isNull( this._xMin ) ) {
		min = getMin( this._xData );
		return ( isNull( min ) ) ? 0.0 : min;
	}
	return this._xMin;
}
Returns the minimum value of the x-axis domain.

@private
@returns {number} minimum value