How to add title to the legend in this barplot in R

Question

I have following data and code to make this barplot:

tt = structure(c(21.5, 19.75, 15.05, 26.925, 19.75, NA, 28.2, 19.7, 
15.4), .Dim = c(3L, 3L), .Dimnames = list(c("4", "6", "8"), c("3", 
"4", "5")))

tt
      3      4    5
4 21.50 26.925 28.2
6 19.75 19.750 19.7
8 15.05     NA 15.4

barplot(tt, beside=T, legend=rownames(tt))

I want to add a title (say "Test") to the legend box. I tried following but it does not work:

barplot(tt, beside=T, legend=rownames(tt), legend.text="Test")

also:

barplot(tt, beside=T, legend=rownames(tt))
legend("topright", legend="test")

Thanks for your help.

Answer 1

You can use the argument args.legend to pass extra arguments to the function legend(), like this:

barplot(tt, beside=TRUE, legend=rownames(tt),args.legend=list(title="aTitle"))

Gives:

Note that you can also pass other arguments of the legend() function in the same way, so you can adjust the appearance further with the arguments you find on the help page ?legend.