[R] Adding bars to barplots

[Kay, Winston]

I'm trying to add stacked bars to a third column of a barplot and using
the following code:

year <- c(2004, 2005, 2006, 2007, 2008)
nlic <- c(5,8,6,4,2)
allow <- c(5,8,6,4,2)
shot <- c(1,6,0,1,0)
farm <- c(0,0,0,0,0)

dfs <-matrix(data=c(nlic, allow), nrow=5, ncol=2)

barplot(t(dfs), beside=T, names.arg=year)


I would then like to add shot+farm stacked bars to a third column of the
preceding plot. I've tried the add argument without much joy. Can anyone
provide sample code?

Thanks

Winston

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