[R] problem with putting objects in list

[Tony Plate]

I suspect you are not thinking about the list and the 
subsetting/extraction operators in the right way.

A list contains a number of components.

To get a subset of the list, use the '[' operator.  The subset can 
contain zero or more components of the list, and it is a list itself. 
So, if x is a list, then x[2] is a list containing a single component.

To extract a component from the list, use the '[[' operator.  You can 
only extract one component at a time.  If you supply a vector index with 
more than one element, it will index recursively.

 > x <- list(1,2:3,letters[1:3])
 > x
[[1]]
[1] 1

[[2]]
[1] 2 3

[[3]]
[1] "a" "b" "c"

 > # a subset of the list
 > x[2:3]
[[1]]
[1] 2 3

[[2]]
[1] "a" "b" "c"

 > # a list with one component:
 > x[2]
[[1]]
[1] 2 3

 > # the second component itself
 > x[[2]]
[1] 2 3
 > # recursive indexing
 > x[[c(2,1)]]
[1] 2
 > x[[c(3,2)]]
[1] "b"
 >

Rainer M Krug wrote:
> Hi
> 
> I use the following code and it stores the results of density() in the
> list dr:
> 
> dens <- function(run) { density( positions$X[positions$run==run], bw=3,
> cut=-2 ) }
> dr <- lapply(1:5, dens)
> 
> but the results are stored in dr[[i]] and not dr[i], i.e. plot(dr[[1]])
> works, but plot([1]) doesn't.
> 
> Is there any way that I can store them in dr[i]?
> 
> Thanks a lot,
> 
> Rainer
> 
> 
>