gnuplot - How to label (x,y) data points in Gnuplot 4.2 with integer numbers

Question

I have a text file with 2 columns of numbers corresponding to (x,y) coords.

4 1
4 5
1 1
1 5
2.5 3

How do I tell gnuplot to plot these points and label each point with its corresponding row #? (Please keep in mind I'm going to apply this to a much larger file with 100 points, so I'm looking for a way to do it automagically, rather than have to create a 3rd column of data corresponding to row numbers).

Answer 1

You can use the with labels flag to the plot command. By default this places the label instead of the point at the place where the point would be. with label takes the offset flag (and any flag you can pass to set label) so you can have the label next to the point. Here is an example script:

#!/usr/bin/env gnuplot

reset

set terminal pngcairo
set output 'test.png'

set xr [0:5]
set yr [0:6]

plot 'data.dat' pt 7, \
     'data.dat' using 1:2:($0+1) with labels offset 1 notitle

which produces this output: