Enhancements to declarative analysis in ROOT

ROOT is a tool used by virtually every High Energy Physics analysis inside and outside CERN, thanks to the range of functionalities offered. RDataFrame is a ROOT component that offers the user an intuitive functional programming interface and gives access to automatic analysis parallelization. The goal of RDataFrame is to make data analysis as efficient, expressive and simple as possible. This report presents the features added on the RDataFrame during the Summer Student Internship to offer an even more powerful tool to the users.