Tgraph with vector inputs not drawing the graph?

Below is the code i am trying to run in command window but it says error “can’t call TGraph” and gives me the list of TGraph types… HELP!!!

int main()
  ifstream inputFile;
  string Line;"data.txt", ios::in);
 while ( getline(inputFile, Line, '\n') )
    vector<string> columns;
    stringstream ss(Line);
    string word;
    while (getline(ss, word, '\t'))    
	TCanvas *c1 = new TCanvas();
	TGraph *g_plot = new TGraph (columns.size(), &columns[0], &columns[1]);

You cannot create a TGraph from a “vector” (see the available constructors in the TGraph class description).

yes thank you i got it have changed string to double.