set key [ <position> ... ] [<xoffset>, <yoffset>]
The setting ‘key’ determines whether a legend is placed on a plot, and if so, where it should be located on the plot. Issuing the command:
set key
simply causes a legend to be added to the plot in its default position, usually the plot’s upper-right corner. The converse action is achieved by:
set nokey
or:
unset key
both of which cause a plot to have no legend. A position for the key may also be specified after the set key command, for example:
set key bottom left
Recognised positions are ‘top’, ‘bottom’, ‘left’, ‘right’, ‘below’, ‘outside’, ‘xcentre’ and ‘ycentre’. In addition, if none of these quite achieved the desired result, a positional offset may be specified after one of the position keywords above. The first value is assumed to be an -offset, and the second a
-offset, in units approximately equal to the size of the plot. For example:
set key bottom left 0.0 -0.5
would display a key below the bottom left corner of the graph.