Making a simple graph from data out of a data file

Dear reader,

Since a short while my partner and I (both secundary school Physics teachers working one day a week on the Hisparc project) are trying to work with ROOT. We are trying to create analysis software with which we can go through a massive database with measuring results from 8 different detectors that have been running for app. 6 years. We have used ROOT succesfully for doing simple HISTOGRAMS on the data (from the Hisparc-project in the Netherlands).
We also used C combined with ROOT to create new files that hold a number of parameters coming from a Landau fit on the histograms.
Our next step is to make graphs of these parameters (MPV,s and errors). But we just can’t seem to manage. Does anybody has an example of a small Root program where data is collected from a file and than turned into a graph?

Many regards,

One of the TGraph constructors has a file name as input parameter.

May be you should also consider using TTree/TNuple.