Filling a divided canvas with multiple TGraphs from within a for loop

[rNov77]

Hi All,

I am trying to get a TGraphErrors plot in each of the sub-divisions of the canvas for comparison. Unfortunately, I get only the last plot in the last subdivision after saving the canvas in a root file. I can see all the plots getting plotted at their destinations while the for loop runs, but at the end only one segment has the plot. Code snippet and canvas image attached below:

 ...
 ck = TCanvas('ck', 'canvas', 800, 800)
 ck.Divide(4,4, 0.001, 0.001)

 for k in range(1, 17):
    arr = np.asarray(p[k-1]).astype(float)      #p = [[] for i in range(16)] populated from a txt file
    volt 	= array('d', arr[:, 1])
    Gain 	= array('d', arr[:, 4])
    Gain_e 	= array('d', arr[:, 5])

    ck.cd(k)
    gr2 = TGraphErrors(70, volt, Gain, zero, Gain_e) #zero is array of zeroes
    gr2.Draw()
    ck.Update()    
    ck.Modified() 

 ck.Write()

What am I doing wrong or is this a wrong approach?

[bellenot]

Try something like this:

    pad = ck.cd(k)
    gr2 = TGraphErrors(70, volt, Gain, zero, Gain_e) #zero is array of zeroes
    gr2.Draw()
    pad.Modified() 
    pad.Update()    

or:

    ck.cd(k)
    gr2 = TGraphErrors(70, volt, Gain, zero, Gain_e) #zero is array of zeroes
    gr2.Draw()
    gPad.Modified() 
    gPad.Update()    

[rNov77]

Tried both. Still the same

[Wile_E_Coyote]

Try:

    gr2 = TGraphErrors(70, volt, Gain, zero, Gain_e) #zero is array of zeroes
    pad = ck.cd(k)
    gROOT.SetSelectedPad(pad)
    gr2.DrawClone()
    pad.Modified()
    pad.Update()

and then:

ck.cd(0)
ck.Write()

[rNov77]

    gr2 = TGraphErrors(70, volt, Gain, zero, Gain_e) #zero is array of zeroes
    pad = ck.cd(k)
    gROOT.SetSelectedPad(pad)
    gr2.DrawClone()                 #gr2.Draw()
    pad.Modified()
    pad.Update()

I get a blank canvas when I put DrawClone() instead of Draw(). Other than that no changes.

I can see each instance of for loop plot a pad with the correct data but rest of them are blank. As the loop progresses the previously drawn pads go blank as well. Last instance of for loop leaves me with the 16th pad plotted. For some reason the previously plotted pads aren’t getting retained with the loop.

[Wile_E_Coyote]

Try:

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As noticed in another thread, the trick with defining “t2” as a list does not help when one resizes or double-clicks the corresponding canvas (all drawn texts disappear). Unfortunately, as written in my first post here, ROOT with python2 will automatically delete “cloned” texts (note: the simple “gROOT.SetSelectedPad(gPad); t2.DrawClone()” sequence seems to work in ROOT with python3). So, I’ve found another brutal fix which works in both python versions. Right in the beginning use: from ROOT…

[rNov77]

Thanks for the help @Wile_E_Coyote and @bellenot

But I may have figured out a solution. I believe the same variable ‘gr1’ for all instances of the loop is causing this problem as it wasn’t getting re-initialized. I made a list of them and it worked. Code and image attached below:

gr = ['gr1', 'gr2', 'gr3', 'gr4', 'gr5', 'gr6', 'gr7', 'gr8', 'gr9',
 'gr10', 'gr11', 'gr12', 'gr13', 'gr14', 'gr15', 'gr16']

for k in range(1, 17):
    arr = np.asarray(p[k-1]).astype(float)      #p = [[] for i in range(16)] populated from a txt file
    volt 	= array('d', arr[:, 1])
    Gain 	= array('d', arr[:, 4])
    Gain_e 	= array('d', arr[:, 5])

    gr[k-1] = TGraphErrors(70, volt, Gain, zero, Gain_e) #zero is array of zeroes
    pad = ck.cd(k)
    gROOT.SetSelectedPad(pad)
    gr[k-1].Draw()
    pad.Modified()
    pad.Update()

ck.cd()
ck.Write()