Я делаю что-то вроде этого
library(data.table)
setDT(dt)
dataGraf <- rbind(data[ ,.(Year, value = Unemployment_Rate, Type = "Unemployment_Rate")],
data[ ,.(Year, value = Inflation_Rate, Type = "Inflation_Rate")],
data[ ,.(Year, value = GDP, Type = "GDP")])
ggplot(dataGraf,aes(Year, value, color = Type))+geom_line()+geom_point()