zeroaxis

The x axis may be drawn by set xzeroaxis and removed by unset xzeroaxis. Similar commands behave similarly for the y, x2, y2, and z axes. set zeroaxis ... (no prefix) acts on the x, y, and z axes jointly.

Syntax:

      set {x|x2|y|y2|z}zeroaxis { {linestyle | ls <line_style>}
                                 | {linetype | lt <line_type>}
                                   {linewidth | lw <line_width>}
                                   {linecolor | lc <colorspec>}
                                   {dashtype | dt <dashtype>} }
      unset {x|x2|y|y2|z}zeroaxis
      show {x|y|z}zeroaxis

By default, these options are off. The selected zero axis is drawn with a line of type <line_type>, width <line_width>, color <colorspec>, and dash type <dashtype> (if supported by the terminal driver currently in use), or a user-defined style <line_style> (see set style line).

If no linetype is specified, any zero axes selected will be drawn using the axis linetype (linetype 0).

Examples:

To simply have the y=0 axis drawn visibly:

       set xzeroaxis

If you want a thick line in a different color or pattern, instead:

       set xzeroaxis linetype 3 linewidth 2.5