set xtics {add} ("label1" <pos1> <level1>, "label2" <pos2> <level2>, ...)
The explicit ("label" 4#4pos5#5 4#4level5#5, ...) form allows arbitrary tic positions or non-numeric tic labels. In this form, the tics do not need to be listed in numerical order. Each tic has a position, optionally with a label.
The label is a string enclosed by quotes or a string-valued expression. It may contain formatting information for converting the position into its label, such as "%3f clients", or it may be the empty string "". See set format (p. ) for more information. If no string is given, the default label (numerical) is used.
An explicit tic mark has a third parameter, the level. The default is level 0, a major tic. Level 1 generates a minor tic. Labels are never printed for minor tics. Major and minor tics may be auto-generated by the program or specified explicitly by the user. Tics with level 2 and higher must be explicitly specified by the user, and take priority over auto-generated tics. The size of tics marks at each level is controlled by the command set tics scale.
Examples:
set xtics ("low" 0, "medium" 50, "high" 100) set xtics (1,2,4,8,16,32,64,128,256,512,1024) set ytics ("bottom" 0, "" 10, "top" 20) set ytics ("bottom" 0, "" 10 1, "top" 20)
In the second example, all tics are labeled. In the third, only the end tics are labeled. In the fourth, the unlabeled tic is a minor tic.
Normally if explicit tics are given, they are used instead of auto-generated tics. Conversely if you specify set xtics auto or the like it will erase any previously specified explicit tics. You can mix explicit and auto- generated tics by using the keyword add, which must appear before the tic style being added.
Example:
set xtics 0,.5,10 set xtics add ("Pi" 3.14159)
This will automatically generate tic marks every 0.5 along x, but will also add an explicit labeled tic mark at pi.