How to use complex function to define a new column using ROOT.RDataFrame

[xiangjun]

Dear experts,

I try to use a little complex function to define a new column using ROOT.RDataFrame,
Now I can achieve it, but it’s a little complex, could you please help me to simplify it ?
The related codes are shown below

FF_file_name = args.FF_name
FF_file_name_2 = args.FF_name2 

ROOT.gInterpreter.Declare(f"""        
using namespace ROOT;      
TFile*f1=new TFile("{FF_file_name}","read");
TH1F*fake_hist=(TH1F*)f1->Get("fake_factor_hist;1");
cout<<"{FF_file_name}"<<" is read"<<endl;
TFile*f2=new TFile("{FF_file_name_2}","read");
TH1F*fake_hist_2=(TH1F*)f2->Get("fake_factor_hist;1");
cout<<"{FF_file_name_2}"<<" is read"<<endl;
     
"""  
)    
ROOT.gInterpreter.ProcessLine("""     
TH1F*fake_hist=(TH1F*)f1->Get("fake_factor_hist;1");
TH1F*fake_hist2=(TH1F*)f2->Get("fake_factor_hist;1");
""")

rdf_filtered = rdf_filtered.Define('fakefactor',f"fake_hist->Interpolate(ph_pt)")

By the way , it x >10 ,I want to use fake_hist to interpolate, but if x<10, I want to use fake_hist_2 to interpolate, Is there any simple way to achieve it?
Many thanks in advance!

[Danilo]

Thanks for this interesting post!

Let me start by saying that we are working hard to pythonise better the interface of RDataFrame: the analysis interface is very powerful, and we are aware that the experience of our users could greatly benefits if some obstacles are removed when it comes to C++ and Python interplay.

This example should show how you can simplify your code: the workaround consists in leveraging a feature of ROOT which allows to access names of objects as if they were pointers.

I hope it helps, perhaps as a start!

FF_file_name = args.FF_name

f1 = ROOT.TFile.Open(FF_file_name)
fake_hist = f1.fake_factor_hist

# Workaround: make the histos known to the interpreter
ROOT.gInterpreter.ProcessLine("auto fh1 = fake_hist")

rdf_filtered = rdf_filtered.Define('fakefactor',f"fh1->Interpolate(ph_pt)")

[xiangjun]

Hi Danilo,

Thank you very much, but I got two issues.

1. input_line_81:2:24: error: variable ‘fake_hist_temp’ declared with deduced type ‘auto’ cannot appear in its own initializer
   auto fake_hist_temp = fake_hist_temp

I used TH1F* to substitute auto, it seems OK.

2. /eos/home-z/zgao/H_to_Zy/samples/root_to_parquet_2_test.py:95: DeprecationWarning: The attribute syntax for TNetXNGFile is deprecated and will be removed in ROOT 6.34. Please use TNetXNGFile[“fake_factor_hist”] instead of TNetXNGFile.fake_factor_hist
   fake_hist_temp = fake_file_1.fake_factor_hist

It seems no problem, is it better to use

fake_file_1["fake_factor_hist"]

[Danilo]

Hi,

Thanks. You do have a point.
I am curious: what ROOT version are you using? The complaint about type deduction is somewhat not expected…

Cheers,
D

[xiangjun]

Hi,
I’m using ROOT 6.32.06