Reading an ASCII file and make a graph

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2

Step 1: Check the documentation http://root.cern.ch/root/html/TGraph.html#TGraph:TGraph@10
Step 2: There is a hint on how to extract specific columns only.

root [3] TGraph g1("test.txt", "%lg %lg")
root [4] TGraph g2("test.txt", "%lg %*lg %lg")
root [5] TGraph g3("test.txt", "%lg %*lg %*lg %lg")
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