Xtics series

Syntax:
    set xtics <incr>
    set xtics <start>, <incr>, <end>
The implicit $<$start$>$, $<$incr$>$, $<$end$>$ form specifies that a series of tics will be plotted on the axis between the values $<$start$>$ and $<$end$>$ with an increment of $<$incr$>$. If $<$end$>$ is not given, it is assumed to be infinity. The increment may be negative. If neither $<$start$>$ nor $<$end$>$ is given, $<$start$>$ is assumed to be negative infinity, $<$end$>$ is assumed to be positive infinity, and the tics will be drawn at integral multiples of $<$incr$>$. If the axis is logarithmic, the increment will be used as a multiplicative factor.

If you specify to a negative $<$start$>$ or $<$incr$>$ after a numerical value (e.g., rotate by $<$angle$>$ or offset $<$offset$>$), the parser fails because it subtracts $<$start$>$ or $<$incr$>$ from that value. As a workaround, specify 0-$<$start$>$ resp. 0-$<$incr$>$ in that case.

Example:

     set xtics border offset 0,0.5 -5,1,5
Fails with 'invalid expression' at the last comma.
     set xtics border offset 0,0.5 0-5,1,5
or
     set xtics offset 0,0.5 border -5,1,5
Sets tics at the border, tics text with an offset of 0,0.5 characters, and sets the start, increment, and end to -5, 1, and 5, as requested.

The set grid options 'front', 'back' and 'layerdefault' affect the drawing order of the xtics, too.

Examples:

Make tics at 0, 0.5, 1, 1.5, ..., 9.5, 10.

     set xtics 0,.5,10

Make tics at ..., -10, -5, 0, 5, 10, ...

     set xtics 5

Make tics at 1, 100, 1e4, 1e6, 1e8.

     set logscale x; set xtics 1,100,1e8