You can plot different columns of the same file like this:
plot 'file' using 0:1 with lines, '' using 0:2 with lines ...
... means continuation). A couple of notes on this notation:
using specifies which column to plot i.e. column 0 and 1 in the first
using statement, the 0th column is a pseudo column that translates to the current line number in the data file. Note that if only one argument is used with
using n) it corresponds to saying
using 0:n (thanks for pointing that out mgilson).
If your Gnuplot version is recent enough, you would be able to plot all 4 columns with a for-loop:
set key outside plot for [col=1:4] 'file' using 0:col with lines
Gnuplot can use column headings for the title if they are in the data file, e.g.:
min max mean std 24 31 29.0909 2.57451 12 31 27.2727 5.24129 14 31 26.1818 5.04197 22 31 27.7273 3.13603 22 31 28.1818 2.88627
set key outside plot for [col=1:4] 'file' using 0:col with lines title columnheader