On Sun, 11 Oct 2009, Ozan Bak???~_ wrote:
Hi R-users,
I would like to calculate weighted mean of several
variables by two factors where the weight vector is
the same for all variables.
Below, there is a simple example where I have only two
variables: "v1","v2" both weighted by "wt" and my factors
are "gender" and "year".
set.seed(1)
df <- data.frame(gender = rep(c("M", "F"),each = 5),
year = rep(c(1999, 2000), 5), v1 = rnorm(10,10),
v2 = rnorm(10,6), wt = runif(10))
df
g <- function(x) weighted.mean(x[, 1], x[, 2])
by(df[,c("v1","wt")],df[,c("year","gender")],g)
I can use as above by command for each variable (v1,v2)
separately but I wonder if there is some simpler way
that yields a table/data frame of weigted means for all
"vi"s where i=1...N.
This is R; There are lots of ways.
Here is one:
lm( cbind( v1, v2 ) ~ 0 + gender:factor(year), df, weight=wt)
Call:
lm(formula = cbind(v1, v2) ~ 0 + gender:factor(year), data = df,
weights = wt)
Coefficients:
v1 v2
genderF:factor(year)1999 10.573 6.795
genderM:factor(year)1999 9.534 6.633
genderF:factor(year)2000 9.741 6.422
genderM:factor(year)2000 10.834 5.190
HTH,
Chuck
Thank you very much,
ozan
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