I have a list that is indexed like the following:

>list.stuff
[[1]]
[[1]]$vector
...
[[1]]$matrix
....
[[1]]$vector

[[2]]
null

[[3]]
[[3]]$vector
...
[[3]]$matrix
....
[[3]]$vector
.
.
.

Each segment in the list is indexed according to another vector of indexes:

>index.list
1, 3, 5, 10, 15

In list.stuff, only at each of the indexes 1,3,5,10,15 will there be 2 vectors and one matrix; everything else will be null like [[2]]. What I want to do is to lag like the lag.xts function so that whatever is stored in [[1]] will be pushed to [[3]] and the last one drops off. This also requires subsetting the list, if its possible. I was wondering if there exists some functions that handle list manipulation.

My thinking is that for xts, a time series can be extracted based on an index you supply:

xts.object[index,]  #returns the rows 1,3,5,10,15

From here I can lag it with:

lag.xts(xts.object[index,])

Any help would be appreciated thanks:

EDIT: Here is a reproducible example:

list.stuff<-list()
vec<-c(1,2,3,4,5,6,7,8,9)
vec2<-c(1,2,3,4,5,6,7,8,9)
mat<-matrix(c(1,2,3,4,5,6,7,8),4,2)

list.vec.mat<-list(vec=vec,mat=mat,vec2=vec2)


ind<-c(2,4,6,8,10)
for(i in ind){
   list.stuff[[i]]<-list.vec.mat
}