This recipe is a simple modification of the previous one, but gets its own section because the legend in the box is such a popular style (for better or worse).
Replace the highlighted
set key command in the previous recipe with the following two commands:
set key spacing 3 font "Helvetica, 14" set key box lt -1 lw 2
The new command is in the second line.
set key box tells gnuplot to draw a box around the legend; this is followed by two specifications for the type of line from which the box will be drawn. In the previous command, we have used abbreviations:
lt stands for linetype, and a linetype ...