This post explains how to add a legend to a chart made with base R,
using the legend()
function. It provides several
reproducible examples with explanation and R
code.
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 #73
horiz
: legend in column or in row
col
: symbol colorpch
: symbol type. See
graph #6
pt.cex
: symbol size
cex
: text sizetext.col
: text color
topright
: 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 axis
You can also give the X
and
Y
coordinate 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))