set autoscale noextend
By default autoscaling sets the axis range limits to the nearest tic label
position that includes all the plot data. Keywords fixmin, fixmax, fix
or noextend tell gnuplot to disable extension of the axis range to the next
tic mark position. In this case the axis range limit exactly matches the
coordinate of the most extreme data point. set autoscale noextend is a
synonym for set autoscale fix. Range extension for a single axis can be
disabled by appending the noextend keyword to the corresponding range
command, e.g.
set yrange [0:*] noextend
set autoscale keepfix autoscales all axes while leaving the fix settings unchanged.