Exercise 2: Add error bars to a histogram

(5 minutes)

We’re still plotting the chi2 histogram as a solid curve. Most of the time, your supervisor will want to see histograms with errors. Revise the Analyze::Terminate method in Analyze.C to draw the histograms with error bars.

Hint

Look back at Working with Histograms.

Warning

The histogram may not be immediately visible, because all the points are squeezed into the left-hand side of the plot. We’ll investigate the reason why in a subsequent exercise.

After you make a change to Analyze.C, you have to restart ROOT before you run tree1->Process("Analyze.C") again. Don’t forget the up-arrow key!

chi2 histogram — Figure 30: What I get when I plot chi2 with errors bars turned on.

Note

See this note in the Python tutorial for how I made this plot.