Converting a Log to Linear Histogram

Newbie
1

Hi all,

I have been trying to convert my log histograms to linear and have been having some difficulty. Once the script is executed, nothing happens. I might be over complicating the script but I have tried the SetLogy() command as well. Any help is appreciated. Thank you :slight_smile:

linear_histogram.C (3.3 KB)

2 
~/carolina/build/8.7MeV_coincidence_gates_labr_labr/gated_coincidences_total_projections/projx$ ./linear_histogram 
Warning in <TFile::Append>: Replacing existing TH1: gate (Potential memory leak).

 *** Break *** segmentation violation



===========================================================
There was a crash.
This is the entire stack trace of all threads:
===========================================================
#0  0x00007f851eeea45a in __GI___wait4 (pid=10602, stat_loc=stat_loc
entry=0x7fffa0aff618, options=options
entry=0, usage=usage
entry=0x0) at ../sysdeps/unix/sysv/linux/wait4.c:30
#1  0x00007f851eeea41b in __GI___waitpid (pid=<optimized out>, stat_loc=stat_loc
entry=0x7fffa0aff618, options=options
entry=0) at ./posix/waitpid.c:38
#2  0x00007f851ee50bcb in do_system (line=<optimized out>) at ../sysdeps/posix/system.c:171
#3  0x00007f8520317494 in TUnixSystem::StackTrace() () from /usr/local/lib/libCore.so
#4  0x00007f8520314795 in TUnixSystem::DispatchSignals(ESignals) () from /usr/local/lib/libCore.so
#5  <signal handler called>
#6  0x0000558cde6e07d2 in DrawLinearHistogram() ()
#7  0x0000558cde6e0c48 in main ()
===========================================================


The lines below might hint at the cause of the crash.
You may get help by asking at the ROOT forum https://root.cern.ch/forum
Only if you are really convinced it is a bug in ROOT then please submit a
report at https://root.cern.ch/bugs Please post the ENTIRE stack trace
from above as an attachment in addition to anything else
that might help us fixing this issue.
===========================================================
#6  0x0000558cde6e07d2 in DrawLinearHistogram() ()
#7  0x0000558cde6e0c48 in main ()
===========================================================

P.S. please use ``` symbols to format your console output

3

Dear @Xavier_James ,

First off, I just wanted to point out that your code contains many new without the corresponding delete. This is recipe for disaster. Please refrain from using this pattern in your C++ code. Instead of new you should use stack-based variables or std::unique_ptr.

That said, I don’t understand what you are trying to do exactly. Your initial post said

I have been trying to convert my log histograms to linear

But I don’t see this being done in the script. The histogram you retrieve from the file with this line

linearHist = (TH1D*)file->Get("gate");

is called linearHist. So I assume it’s already “linear” and you don’t need to convert it “from log to linear”.

Second, the stack trace you provide in your second post doesn’t tell us a lot, since you are probably not using a ROOT build with debug symbols enabled (and that’s not really the point here), but it may very well be just due to usage of a dangling pointer or use-after-free (again another point in favor of discouraging the use of new in your code).

SetLogy() should be probably called on the canvas, directly after creation

TCanvas c;
c.SetLogy();

But again, I’m not sure that’s what you are trying to do in the first place. Let me know.

Cheers,
Vincenzo

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