Syntax:
set style increment {default|userstyles}
show style increment
By default, successive plots within the same graph will use successive linetypes from the default set for the current terminal type. However, choosing `set style increment user` allows you to step through the user-defined line styles rather than through the default linetypes.
Example:
set style line 1 lw 2 lc rgb "gold"
set style line 2 lw 2 lc rgb "purple"
set style line 4 lw 1 lc rgb "sea-green"
set style increment user
plot f1(x), f2(x), f3(x), f4(x)
should plot functions f1, f2, f4 in your 3 newly defined line styles. If a user-defined line style is not found then the corresponding default linetype is used instead. E.g. in the example above, f3(x) will be plotted using the default linetype 3.