15.58.2.5 TOP...
- Produces only a single axes at the TOP according to n1,n2.... You may also produce the axes to the LEFT,RIGHT, or BOTTOM. For 1-d plot X produces both TOP and BOTTOM axes, Y produces both LEFT and RIGHT, while Z produces only TOP. On 3-d plots they produce X,Y, or Z axes. The axes are not produced if disabled by the SET AXES command. After this option the tick values are assumed to be LABELS LONG.