Neat! Thanks.


On 10/5/07, Deepayan Sarkar <deepayan.sarkar@gmail.com> wrote:
>
> On 10/5/07, born.to.b.wyld@gmail.com <born.to.b.wyld@gmail.com> wrote:
> > I have an application that would generate a cross-tabulation in array
> > format in R. In particular, my application would give me a result
> > similar to that of :
> >
> > array(5,c(2,2,2,2,2))
> >
> > The above could be seen as a cross-tabulation of 5 variables with 2
> > levels each (could be 0 and 1). In this case, the data were such that
> > each cell has exactly 5 observations. I
> >
> > Now, I want the output to look like the output of 'xtabs' utility, so
> > that I can use this output inside 'loglm(MASS)'. In particular, I want
> > to add (variable) names to each dimension and indicate the levels that
> > correspond to each cell. The output from 'xtabs' for a data set of
> > this kind would look like:
>
> Simplifying your example:
>
> > foo <- array(5,c(2,2), dimnames = list(xx = c("x=0", "x=1"), yy = c("A",
> "B")))
> > foo
>      yy
> xx    A B
>   x=0 5 5
>   x=1 5 5
>
> You can also do this in two steps:
>
> foo <- array(5,c(2,2))
> dimnames(foo) <-  list(xx = c("x=0", "x=1"), yy = c("A", "B"))
>
> [...]
>
> > Now, I do not generate my output using the 'xtabs' utility. In fact,
> > my simulations would generate the cross-table directly and not the
> > dataset.
> >
> > Can anyone help? R examples have some reference to the 'dimnames'
> > attribute, but I am not exactly sure.
> > Also, is there an R function that could do the exact opposite of
> > 'xtabs', that is, may be generate a data frame given its cross-table?
>
> Sort of (there is only one column for each combination, giving
> `frequencies'):
>
> > as.data.frame.table(foo)
>    xx yy Freq
> 1 x=0  A    5
> 2 x=1  A    5
> 3 x=0  B    5
> 4 x=1  B    5
>
> If foo has class "table", then as.data.frame(foo) would also work.
>
> -Deepayan
>

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