[R] recoding table dimensions interactively

[Hadley Wickham]

Hi Michael,

It's pretty easy with reshape:

library(reshape2)
ucbm <- melt(UCBAdmissions)
acast(ucbm, Admit + Gender ~ Dept)
acast(ucbm, Admit ~ Dept + Gender)
acast(ucbm, Admit + Dept + Gender ~ .)

# You can also do aggregations
acast(ucbm, Admit ~ Dept, fun = sum)

Hadley

On Thu, Jan 9, 2014 at 9:14 AM, Michael Friendly <friendly at yorku.ca> wrote:
> Given a 3+ way table, I'd like a simple, elegant way to flatten the table to
> a two-way
> table, with some variables joined interactively to form the rows and others
> forming
> the columns.  For example, starting with
>
>> str(UCBAdmissions)
>  table [1:2, 1:2, 1:6] 512 313 89 19 353 207 17 8 120 205 ...
>  - attr(*, "dimnames")=List of 3
>   ..$ Admit : chr [1:2] "Admitted" "Rejected"
>   ..$ Gender: chr [1:2] "Male" "Female"
>   ..$ Dept  : chr [1:6] "A" "B" "C" "D" ...
>>
>
> What I want is something similar to the result of ftable:
>
>> ftable(UCBAdmissions)
>                 Dept   A   B   C   D   E   F
> Admit    Gender
> Admitted Male        512 353 120 138  53  22
>          Female       89  17 202 131  94  24
> Rejected Male        313 207 205 279 138 351
>          Female       19   8 391 244 299 317
>
> One way to do this is to convert to a data.frame, paste the factors together
> and then convert back to a table:
>
> UCB.df <- as.data.frame(UCBAdmissions)
> UCB.df$`Admit:Gender` <- paste(UCB.df$Admit, UCB.df$Gender, sep=':')
> UCB.tab2 <- xtabs(Freq ~ `Admit:Gender` + Dept, data=UCB.df)
> UCB.tab2
>
>> UCB.tab2
>                  Dept
> Admit:Gender        A   B   C   D   E   F
>   Admitted:Female  89  17 202 131  94  24
>   Admitted:Male   512 353 120 138  53  22
>   Rejected:Female  19   8 391 244 299 317
>   Rejected:Male   313 207 205 279 138 351
>>
>
> But maybe there is a simpler, more elegant and general way to do this.
>
> --
> Michael Friendly     Email: friendly AT yorku DOT ca
> Professor, Psychology Dept. & Chair, Quantitative Methods
> York University      Voice: 416 736-2100 x66249 Fax: 416 736-5814
> 4700 Keele Street    Web:http://www.datavis.ca
> Toronto, ONT  M3J 1P3 CANADA
>
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