Recovering data points using g3data

A very nice free, (GNU GPL) application that can be used for extracting data from graphs is g3data. You can install it in ubuntu by typing:
$ sudo apt-get install g3data
or simply download it from the g3data website http://www.frantz.fi/software/g3data.php

I have used it a few times in the past on graphs of different kind and quality and always obtained good results for the extracted data points using it.
The following picture shows g3data at work on a plot:

When the data are recovered you can store them in a file and use your favorite tool to create a new plot.