[R] "Reversal" of Aggregation

[Achim Zeileis]

On Mon, 29 Jan 2007, Roland Rau wrote:

> Dear all,
>
> given I have a data.frame in a format like this
>
> mydf <- data.frame(age=rep(1:3,5),
>                    year=c(rep(1996,3), rep(1997,3), rep(1998,3),
>                      rep(1999,3), rep(2000,3)),
>                    income=1:15)
> mydf
>
>
> Now I convert it to some 2D-frequency table like this:
> mymatrix <- tapply(X=mydf$income, INDEX=list(mydf$age, mydf$year),
>                    FUN=sum)
> mymatrix
>
>
> My question is:
> How can I go the opposite way, i.e. from 'mymatrix' to 'mydf'?
> Is there an elegant way?

You could do
  as.data.frame(as.table(mymatrix))
and then set appropriate column names. (The first two variables are also
coded as "factor"s which might or might not be what you want in this
example.)

Z


> Thanks,
> Roland
>
> 	[[alternative HTML version deleted]]
>
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