This page aims to explain how to add a legend to a plot made in base R. It is done using the legend() function. The main arguments are:
legend: names to displaybty: type of box around the legend. See graph #73horiz: legend in column or in rowcol: symbol colorpch: symbol type. See graph #6pt.cex: symbol sizecex: text sizetext.col: text colortopright: legend position:bottomright,bottom,bottomleft,left,topleft,top,topright,right,center.inset: % (from 0 to 1) to draw the legend away from x and y axisYou can also give the
XandYcoordinate of the legend:legend(3, 5, ...)
Note that an equivalent page exist concerning legends with ggplot2.
# Create data:
a=c(1:5)
b=c(5,3,4,5,5)
c=c(4,5,4,3,1)
# Make a basic graph
plot( b~a , type="b" , bty="l" , xlab="value of a" , ylab="value of b" , col=rgb(0.2,0.4,0.1,0.7) , lwd=3 , pch=17 , ylim=c(1,5) )
lines(c ~a , col=rgb(0.8,0.4,0.1,0.7) , lwd=3 , pch=19 , type="b" )
# Add a legend
legend("bottomleft",
legend = c("Group 1", "Group 2"),
col = c(rgb(0.2,0.4,0.1,0.7),
rgb(0.8,0.4,0.1,0.7)),
pch = c(17,19),
bty = "n",
pt.cex = 2,
cex = 1.2,
text.col = "black",
horiz = F ,
inset = c(0.1, 0.1))
