[R] how to do by-processing using weighted.mean

[Thomas Lumley]

On Sun, 9 Jan 2005, Denis Chabot wrote:

> Hi,
>
> I'd like to compute the weighted mean of some variables, all using the same 
> weight variable, for each combination of 3 factor variables.
>
> I found how I could use "summarize" (from Hmisc) to do normal means for 
> combinations of 3 factors, but I cannot find a way of doing weighted means. 
> Is it possible in R?

?weighted.mean

 	-thomas