set logscale <axes> <base>
unset logscale <axes>
show logscale
where <axes> may be any combinations of `x`, `x2`, `y`, `y2`, `z`, and `cb` in any order, and where <base> is the base of the log scaling. If <base> is not given, then 10 is assumed. If <axes> is not given, then all axes are assumed. The command logscale turns off log scaling for the specified axes.
Examples:
To enable log scaling in both x and z axes:
set logscale xz
To enable scaling log base 2 of the y axis:
set logscale y 2
To enable z and color log axes for a pm3d plot:
set logscale zcb
To disable z axis log scaling:
unset logscale z