axis.num_labels = Math.round( size / axis.label_spacing );
if ( axis.num_labels > axis.range ) axis.num_labels = axis.range;
axis.inc = Math.ceil( axis.range / axis.num_labels );
axis.num_labels = Math.round( size / axis.label_spacing );
if ( axis.num_labels > axis.range ) axis.num_labels = axis.range;
axis.inc = Math.ceil( axis.range / axis.num_labels );