For ROOT users

Many previous VHE gamma-ray developers are familiar with the CERN ROOT library for data processing. ctapipe is intentionally not ROOT based, and we do not allow ROOT or pyroot as a required dependency of ctapipe due to its large and complex nature and maintenence issues. Fortunately nearly all ROOT-like functionality can be found in the scientific python stack, though the API is of course not the same.

To help developers familiar only with ROOT migrate to the scientific python stack, the following table can be helpful:

ROOT functionality	Recommended Python Equivalent
interactive interpreter	ipython, jupyter notebook
TH1D,TH2D,TH3D	numpy.ndarray + numpy.histogramdd()
TProfile	numpy.ndarray
TGraph	numpy.ndarray + matplotlib plots
TTree	astropy.table, pandas, pytables
ROOT File format (TFile)	HDF5 (pytables)
TMinuit	scipy.optimize or iminuit
2D/3D graphics	matplotlib or bokeh
TMVA	scikit-learn
GUI	various (wxwidgets, Qt,gtk)
AstroROOT	astropy.io.fits or fitsio
ROOFit	astropy.modelling or lmfit
Reflex, CINT	not needed
TMatrix, etc	numpy.ndarray + scipy.linalg
TMatrixTSparse	scipy.sparse
TList	list
TArray, TObjArray	list
TMap, THashList	dict
TRandom	numpy.random + scipy.stats
Math, MathMore	numpy + scipy
Script compilation	Numba, Cython
ROOT::Math::VirtualIntegrator	scipy.integrate
Access to external C++ code	cython, ctypes
–	astropy.coordinates
–	astropy.units
–	astropy.time
–	astropy.wcs (projections)
–	numpy.ndarray (n-dimensional tables)
–	scipy.interpolate.interpnd (n-dimensional interpolation)
–	scipy.signal (digital signal processing)