[R] cross tabulate variables by subject id

[Michael Bedward]

Hi Marianne,

How about this...

ac.ad <- unstack(dat1, choice ~ cond1:cond2)[, c("A.C", "A.D")]
acad.xtab <- with(ac.ad, table(A.C, A.D))

Michael


On 29 November 2010 20:18, Marianne Promberger
<marianne.promberger at kcl.ac.uk> wrote:
> Dear list,
>
> I have data like this:
>
> dat1 <- data.frame(subject=rep(1:10,2),
>                   cond1=rep(c("A","B"),each=5),
>                   cond2=rep(c("C","D"),each=10),
>                   choice=sample(0:1,10,replace=TRUE))
>
> I would like to compare subjects' "choice" for (cond1=="A" &
> cond2=="C") vs (cond1=="A" & cond2=="D"), using mcnemar.test
>
> The ?mcnemar.test example has the data in a matrix:
>
>     Performance
>            2nd Survey
> 1st Survey   Approve Disapprove
>  Approve        794        150
>  Disapprove      86        570
>
>
> So for my case, I need something like:
>
>   Choice
>         AC
> AD       0      1
>  0     ...
>  1
>
> Where "..." would be the sum of subjects who answered 0 or 1 to AC
> and/or AD respectively.
>
> I can get the first step by making an extra variable:
>
> dat1$condnew <- paste(dat1$cond1,dat1$cond2,sep="")
>
> although I am sure there are more elegant ways, and especially, I am
> stumped how to fill in the cells of the table.
>
> Thanks,
>
> Marianne
>
> --
> Marianne Promberger PhD, King's College London
> http://promberger.info
> R version 2.12.0 (2010-10-15)
> Ubuntu 9.04
>
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