Implementing suggestions for better evaluation of energy-dependent theta cuts

[chaimain]

With taking suggestions from #997 to redefine the "100% range of gamma events" to be used to evaluate percentile cuts on theta value of events, and adding the following -

• An event filter function to take only those with the same disp_sign value after reconstruction (applied to only MC).
• New variable in DL3Cuts component: max_theta_range to create a custom maximum limit of theta value to be considered as "100% of central PSF region", based on which, percentile cuts can be evaluated for each reco_energy bins

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01 🎉

Comparison is base (66ef7f9) 74.36% compared to head (18d6386) 74.37%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1035      +/-   ##
==========================================
+ Coverage   74.36%   74.37%   +0.01%     
==========================================
  Files         124      124              
  Lines       12163    12170       +7     
==========================================
+ Hits         9045     9052       +7     
  Misses       3118     3118              

Impacted Files	Coverage Δ
lstchain/io/io.py	79.19% <ø> (ø)
lstchain/io/event_selection.py	100.00% <100.00%> (ø)
lstchain/io/tests/test_eventselection.py	100.00% <100.00%> (ø)

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[rlopezcoto]

@chaimain after discussing in private, I think this PR can be closed, right?

[chaimain]

@chaimain after discussing in private, I think this PR can be closed, right?

Sorry, I couldn't recheck it yet. Will do it today

[chaimain]

After discussing with @moralejo, I have removed the max_theta_range implementation for limiting the 'max' theta range for evaluating percentile cuts, and as the comparison of disp_sign is only essential in this context for the MC data, I moved that functionality to the function energy_dependent_theta_cuts, as the default option in the function, using the boolean use_same_disp_sign. One can choose not to perform such a selection with this boolean argument.