[R] Titles in plots generated within tapply

[Prof Brian Ripley]

On Wed, 1 Feb 2006, Dennis Malandro wrote:

> How would one go about putting titles in each of several plots
> that are generated from within a call to tapply?  For example I'd
> like the following two barplots to have titles 'Group 1' and
> 'Group 2', where '1' and '2' come from the levels of 'group'.
>
> group <- gl(2, 10)
> result <- sample(c('A', 'B'), size=length(group), replace=TRUE)
> windows(7, 4)
> par(mfrow = c(1, 2))
> tapply(result, group,
>       function(x) barplot(table(x), xlab = 'Result'))

You don't need tapply here (it is just lapply on split). Try

X <- split(result, group)
for(i in levels(group))
     barplot(table(X[[i]]), xlab = 'Result', main = paste("Group", i))

You could use lapply() rather than for(), but there would be no 
benefit.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
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