docs: function xBarPadding() {
  		var domain = xBar.domain();
  		var barSpacing = (domain.length > 1 
  			? (xBar(domain[1]) - xBar(domain[0])) 
  			: xBar.rangeBand());
  		var barPadding = (barSpacing - xBar.rangeBand());
  		return barPadding;
  	}