[R] weight cases?

[Adrian Dusa]

Thanks for this Gabor,

Sometimes weights can take various values, like 0.9
> rep(letters[1:3], c(1, 0.9, 1.6))
[1] "a" "c"

What if the weight variable would be:

my.data$weight <- c(0.4, 2, 1.3, 0.9, 1)

The way I found the solution was to compute the unweighted table, then find 
the weight for each unique combination and multiply that with the 
corresponding row-column entry in the table. The solution though is not very 
satisfactory:

my.data$var1 <- as.factor(my.data$var1)
my.data$var2 <- as.factor(my.data$var2)
total <- expand.grid(levels(my.data$var1), levels(my.data$var2))
rowsmy.data <- apply(unique(my.data[,1:2]), 1, paste, collapse="")
rowstotal <- apply(total, 1, paste, collapse="")
total$weight <- 0
total$weight[sapply(rowsmy.data, function(x) which(rowstotal == x))] <- 
unique(my.data)[,3]

(unweighted <- table(my.data$var1, my.data$var2))
round(unweighted*total$weight, 0)


Yet another question: how would the weight variable be applied to correlate 
two numerical variables?

Best,
Adrian

On Saturday 14 October 2006 16:00, Gabor Grothendieck wrote:
> Try this:
>
>     table(lapply(my.data, rep, my.data$weight)[1:2])
>
> On 10/14/06, Adrian Dusa <dusa.adrian at gmail.com> wrote:
> > Dear all,
> >
> > This is probably a stupid question for which I have a solution, which
> > unfortunately is not as straighforward as I'd like. I wonder if there's a
> > simple way to apply a weighting variable for the cases of a dataframe
> > (well I'm sure there is, I just cannot find it).
> >
> > My toy example:
> > > my.data <- data.frame(var1=c("c", "e", "a", "d", "b"),
> >
> >                        var2=c("E", "B", "A", "C", "D"),
> >                        weight=c(1, 2, 1, 1, 1))
> >
> > > table(my.data$var1, my.data$var2)
> >
> >    A B C D E
> >  a 1 0 0 0 0
> >  b 0 0 0 1 0
> >  c 0 0 0 0 1
> >  d 0 0 1 0 0
> >  e 0 1 0 0 0
> >
> > Applying the weight variable, the table should yield a value of 2 for the
> > "eB"
> >
> > combination:
> > > table(my.data$var1, my.data$var2)
> >
> >    A B C D E
> >  a 1 0 0 0 0
> >  b 0 0 0 1 0
> >  c 0 0 0 0 1
> >  d 0 0 1 0 0
> >  e 0 2 0 0 0
> >
> >
> > Thanks in advance,
> > Adrian
> >
> > --
> > Adrian Dusa
> > Romanian Social Data Archive
> > 1, Schitu Magureanu Bd
> > 050025 Bucharest sector 5
> > Romania
> > Tel./Fax: +40 21 3126618 \
> >          +40 21 3120210 / int.101
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html and provide commented,
> > minimal, self-contained, reproducible code.

-- 
Adrian Dusa
Romanian Social Data Archive
1, Schitu Magureanu Bd
050025 Bucharest sector 5
Romania
Tel./Fax: +40 21 3126618 \
          +40 21 3120210 / int.101