Vectorize is defined to return a function that acts as if 'mapply' was
called.
So we have:
> mapply(dput,1:2) # mapply form
1L # calls dput on each element of 1:2
2L
[1] 1 2
> Vectorize(dput)(1:2) # Vectorize form
1L # same behavior
2L
[1] 1 2
Same thing with a named argument:
> mapply(function(a)dput(a),1:2)
1L
2L
[1] 1 2
> Vectorize(function(a)dput(a))(1:2)
1L
2L
[1] 1 2
But though mapply has no problem with function(...):
> mapply(function(...)dput(list(...)),1:2)
list(1L)
list(2L)
[[1]]
[1] 1
[[2]]
[1] 2
> mapply(function(...)dput(list(...)),1:2,11:12)
list(1L, 11L)
list(2L, 12L)
[,1] [,2]
[1,] 1 2
[2,] 11 12
Vectorize fails silently in this case:
> Vectorize(function(...)dput(list(...))(1:2)
list(1:2) # calls dput with entire vector
# invisible result inherited from dput
> Vectorize(function(...)dput(list(...)))(1:2,11:12)
list(1:2, 11:12)
and sure enough:
> Vectorize(function(...)list(...))
function(...)list(...) # returns arg unmodified!
I looked at the code, and ... args are *explicitly* rejected. I see no
logical reason for this inconsistency, and the documentation doesn't require
it.
-s
PS This is not an artificial example concocted to demonstrate
inconsistencies. I had written the following function which wraps another
function in a tryCatch:
catcher <- function(f) function(...)
tryCatch(do.call(f,list(...)),error=function(e) NA)
(The '...' argument list allows this to work with a function of any number
of arguments.)
but instead of catching individual errors in
Vectorize(catcher(fun))(1:10,1:10), it caught them all as one big error,
which was not at all the goal.
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