Adding a legend to a plot

July 20, 2009

(This article was first published on Learning R, and kindly contributed to R-bloggers)

It's pretty easy!

plot (c(1968,2010),c(0,10),type="n", # sets the x and y axes scales

xlab="Year",ylab="Expenditures/GDP (%)") # adds titles to the axes

lines(year,defense,col="red",lwd=2.5) # adds a line for defense expenditures

lines(year,health,col="blue",lwd=2.5) # adds a line for health expenditures

legend(2000,9.5, # places a legend at the appropriate place c("Health","Defense"), # puts text in the legend

lty=c(1,1), # gives the legend appropriate symbols (lines)

lwd=c(2.5,2.5),col=c("blue","red")) # gives the legend lines the correct color and width