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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