On Feb 4, 2010, at 9:56 AM, J. R. M. Hosking wrote:
sjaffe wrote:
I'm sure I can put this together from the various 'apply's and
split, but I
wonder if anyone has a quick incantation:
E.g. I can do tapply( data, groups, mean)
but how can I do something like: tapply( list(data,weights), groups,
weighted.mean ) ?
(or: mapply is to sapply as ? is to tapply )
Thanks for your help.
coef(lm(data ~ -1 + as.factor(groups), weights=weights))
Not the fastest, but IMO more comprehensible than the constructions
involving anonymous functions.
Are you sure? (Am I sure?) Thomas Lumley has corrected my
misinterpretations on this point (and I apologize to him for the fact
that he has had to do it more than once.)
https://stat.ethz.ch/pipermail/r-help/2010-February/226536.html
I am guessing that the OP was using either sampling weights or
replication weights (he did not say), so lm( , weights) might not be
appropriate tool.
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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