exercise

library(datasets)
dat <- datasets::UCBAdmissions
str(dat)

##  'table' num [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" ...

dat[,1,]

##           Dept
## Admit        A   B   C   D   E   F
##   Admitted 512 353 120 138  53  22
##   Rejected 313 207 205 279 138 351

dat[,1,1]

## Admitted Rejected 
##      512      313

dat[1,1,]

##   A   B   C   D   E   F 
## 512 353 120 138  53  22