TGraphAsymmErrors
TGraphAsymmErrors is a class in the ROOT data analysis framework designed to represent a graph with asymmetric error bars on each data point. It stores, for every point, the coordinates x[i] and y[i], along with four error values: exl[i] and exh[i] for the left and right x-errors, and eyl[i] and eyh[i] for the lower and upper y-errors.
The class derives from TGraph and extends it with per-point asymmetric uncertainties. Points are added or modified
Usage typically mirrors that of other ROOT graph classes, but with the ability to specify different error
TGraphAsymmErrors is contrasted with TGraphErrors, which stores only symmetric errors. It is particularly useful in analyses