Draw a line in a canvas

ROOT
1

Hi,

I am puzzled that I do not manage to draw a simple line in a canvas. Attached is a macro, which should draw a colz plot and a line over that. If I turn off the hDef.Draw(“colz”) and just try to draw the line,

   #hDef.SetMaximum(yMax)
    #hDef.SetMinimum(yMin)
    #hDef.Draw("colz")
    chosenEff = 86.0
    line = TLine(chosenEff,yMin,chosenEff,yMax);
    line.SetLineColor(kYellow)
    line.SetLineWidth(2)
    line.Draw()

I just end up with an empty canvas. What am I doing wrong, I wonder?

Thanks,
Maiken
negativity_plotter.py (3.18 KB)

2

Maiken,

to draw a line, the canvas needs to have a coordinate system to place the line in. Call “c1.Range( 0., -100., 100., 100. )” for example to see the line show up (I came up with those numbers based on the actual values of the TLine’s coordinates in your script).

HTH,
Wim

3

Fantastic! Thank you very much. The magic lines were these:

chosenEff = 0.86
c1.Update()
c1.Range( 0., -10., 1., 10. )
line = TLine(chosenEff,yMin,chosenEff,yMax);
line.SetLineColor(kYellow)
line.SetLineWidth(2)
line.Draw()

negativity.png596×572 10.1 KB