R devel - Dec 2021 - Documentation of addmargins

Dear list,

There is a minor typo in addmargins (section Details):

- If the functions used to form margins are not commutative the result depends
on the order in which margins are computed. Annotation of margins is done via
naming the FUN list.
+ If the functions used to form margins are not commutative**add ':' or
', i.e.' here** the result depends on the order in which margins are
computed. Annotation of margins is done via naming the FUN list.


I'm not sure if such minor things really need to be reported when they are
noticed... Please let me know if not. Of course this is minor, but imho one of
the strengths of R is also its documentation!

Best,

Thomas

Thomas SOEIRO wrote:
> Dear list,
> There is a minor typo in addmargins (section Details):
> - If the functions used to form margins are not commutative the result
depends on the order in which margins are computed. Annotation of margins is
done via naming the FUN list.
> + If the functions used to form margins are not commutative**add
':' or ', i.e.' here** the result depends on the order in which
margins are computed. Annotation of margins is done via naming the FUN list.
>
>
> I'm not sure if such minor things really need to be reported when they
are noticed... Please let me know if not. Of course this is minor, but imho one
of the strengths of R is also its documentation!
>
The documentation looks correct to me.
If the function FUN is not commutative (i.e. the result depends on the order of
the vector passed to it), then the result of addmargins() will depend on the
order of the 'margin' argument to the addmargins() function.

For instance:
mat <- rbind(c(1,10),c(100,1000))
fun <- function(x) {x[1]-x[2]-x[1]*x[2]} # non-commutative function
a <- addmargins(mat ,margin=c(1,2), FUN=fun)
b <- addmargins(mat ,margin=c(2,1), FUN=fun)

a and b are different, because the fun function is not commutative.

-- 
Sincerely
Andr? GILLIBERT