Exploratory data analysis is important, everybody knows that. With R, it is also easy. Below you see three lines of code that allow you to interactively explore the Preston Curve, the prominent association of country level real income per capita with life expectancy.
wb <- read.csv("https://joachim-gassen.github.io/data/wb_condensed.csv")
ExPanD(wb, cs_id = "country", ts_id = "year")
After running these three lines of code (OK, four if you have to install the ExPanDaR package first), a shiny window will open, allowing you to explore a country-year panel of World Bank data and looking something like this.