Hello to all.
My question is very simple...
Let's say we have a data frame with three variables (columns): X, W and F. X
is a numeric variable (e.g. like income) F is a factor (e.g. with 2 levels)
and W is a case weight (data are from household sample but an individual was
interviewed, weights are functions of number of persons in the house hold).
I wanted to compute a means of X weighted by W within groups defined by F
with the function below:
wmean <- function(x,w)
{
wm <- sum( x*w/sum(w) )
wm
}
used within tapply() function, like:
tapply(x,f,wmean,w=w)
but I received some values with 2 warnings:
Warning messages:
1: longer object length
is not a multiple of shorter object length in: x * w
2: longer object length
is not a multiple of shorter object length in: x * w
What is the right way to get the results (how to use 2-argument function in
tapply()), or maybe there is another simple way to do this
ThankYouInAdvance
Michal Bojanowski
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"Michal Bojanowski" <buoy at wp.pl> writes:> Hello to all. > > My question is very simple... > > Let's say we have a data frame with three variables (columns): X, W and F. X > is a numeric variable (e.g. like income) F is a factor (e.g. with 2 levels) > and W is a case weight (data are from household sample but an individual was > interviewed, weights are functions of number of persons in the house hold).> I wanted to compute a means of X weighted by W within groups defined by F > with the function below: > > wmean <- function(x,w) > { > wm <- sum( x*w/sum(w) ) > wm > } > > used within tapply() function, like: > > tapply(x,f,wmean,w=w) > > but I received some values with 2 warnings: > > Warning messages: > 1: longer object length > is not a multiple of shorter object length in: x * w > 2: longer object length > is not a multiple of shorter object length in: x * w > > What is the right way to get the results (how to use 2-argument function in > tapply()), or maybe there is another simple way to do thisIf you start with a data frame you should probably consider using split to produce a list of subframes then lapply. For example, lapply(split(frm, frm$f), function(fr) wmean(fr$x, fr$w)) -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
"Michal Bojanowski" <buoy at wp.pl> writes:> I wanted to compute a means of X weighted by W within groups defined by F > with the function below: > > wmean <- function(x,w) > { > wm <- sum( x*w/sum(w) ) > wm > }(Now whatever was wrong with weighted.mean()??)> used within tapply() function, like: > > tapply(x,f,wmean,w=w) > > but I received some values with 2 warnings: > > Warning messages: > 1: longer object length > is not a multiple of shorter object length in: x * w > 2: longer object length > is not a multiple of shorter object length in: x * w > > What is the right way to get the results (how to use 2-argument function in > tapply()), or maybe there is another simple way to do thisA couple of ways, none really pretty: c(by(dataframe,f, function(d) evalq(wmean(x,w), d))) or equivalently c(by(dataframe,f, eval, expr=quote(wmean(x,w)))) or more directly ind<-seq(along=x) tapply(ind, f, function(i) wmean(x[i],w[i])) And of course tapply(x*w, f, sum) / tapply(w, f, sum) -- O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._