Meaning of fMaximum and fMinimum for TGraph

ROOT
1

Hello,
in the doc of TGraph, one reads

[quote]Double_t fMaximum Maximum value for plotting along y
Double_t fMinimum Minimum value for plotting along y[/quote]

How I understand that is that fMaximum contain the highest value among all the points of the TGraph
For example, if I do

float x[3] = {0,1,2}; float y[3] = {10, 20, 30}; TGraph *g = new TGraph (3,x,y); cout << g->GetMaximum() <<endl;
I expect to get 30
However, I get -1111 as for GetMinimum().
Am I misunderstood the doc or is there a bug?
In the first case, is there a way to get automatically the highest/lowest value of a set of points in a TGraph?

Thank you in advance.

2

This are the min and max value you set using SetMinimum and SetMaximum (from the underlying histogram defining the frame). -111 means they have not been set.
To get the Min and Max it is enough to get the min and max of the vectors in the graph (GetX(), GetY())

3

Thank you for the answer. I was confused with the mix between TGraph and TH1 (or TFrame).