Drawing two added TGraphs while looping over several variables

[mark1]

Hi all,
I am trying to add two TGraphs for each variable I loop over. I tried the following:

c=ROOT.TCanvas('c','c',500,500)
for var in variables:
     
        ['tgraph1_%s'%var].Draw('apc')
	['tgraph2_%s'%var].Draw('SAME')

        c.cd()
	c.Modified()
	c.Update()
	c.SaveAs('test.png')

However, this adds all the graphs together, whereas I only want one graph (with two lines) for each variable. How can I do that?

Cheers

[couet]

I am not sure I fully understand you macro. In the loop you first draw a graph redefining the axes (option “a”) and then a graph on top (by the way "same: is not a graph option use “pc” instead). so at te end of the loop you should see only two graphs.

[mark1]

Thanks! This seems to work, but it seemst to adapt the scale to the first TGraph, so that the second one is not shown. How can I manually change the range?

[couet]

You need to use the class TMultiGraph

[mark1]

I tried that before, but If I do

        mg.Add( ['tgraph1_%s'%var])
	mg.Add( ['tgraph2_%s'%var])
	mg.Draw('apc')

	c.cd()
	c.Modified()
	c.Update()
	
	

It again adds up every graph of each variable in one plot…

[couet]

@mark1

It again adds up every graph of each variable in one plot…

Just put the graphs you need inside the multigraph and it will plot only those. I think you should revisit the logic of your loop.

[mark1]

Right, so there is no way to just “clear” the multigraph?

[couet]

@mark1

Right, so there is no way to just “clear” the multigraph?

It would be better to make sure it is properly filled. But, yes there is a way:

mg->GetListOfGraphs()->Clear();