Labels with matplot

Question

I created a plot with multiple lines using matplot:

matplot(a, cbind(b,c,d,e), pch=1)

where the arguments of cbind are functions of a, for example

b <- 2a+3
c <- 3a+2

and so forth.

How do add the corresponding labels to the resulting lines?

Solution

Sure, how about this?

a <- rnorm(100)
b <- 2*a + 3
c <- 3*a + 2
matplot(a, cbind(b,c), pch=1, col=c(2,4))
legend("bottomright", inset=.05, legend=c("b", "c"), pch=1, col=c(2,4), horiz=TRUE)

Brief explanations:

• bottomright is the location of the legend. you can use coordinates instead.
• insett is a distance from margin
• lengend, pch, and col arguments specify the content and style of the legend
• horz makes the legend displayed horizontally (suitable for short variable names)