R help - Sep 2002 - Problem with indexing

Dear List

I am having a bit of a problem getting a program to work.

For each of i=1 to n persons I have a matrix (different for each person) with 
m rows.

What I want to do, is create m new data sets such that the first is made up 
of the first row for each person from the original matrices, the second 
contains the second row for each person from the original matrices etc etc up 
to the mth new set containing the mth row from the original matrices for each 
person.

Say the original matrix for each person can be indexed by xfinal.list[[i]]

I want to extract for each person in turn, the jth row, i.e. 
xfinal.list[[i]][j,] then bind these n vectors into a new matrix.

I am a little confused as to how I can index the jth row from the ith person, 
obviously I will need a loop 

I thought I would be able to use something like:

for (j in 1:m) {
for (i in 1:n) {
vector.list[[i,j]]<-xfinal.list[[i]][j,]
} }

However I get the error that [[]] is an improper number of subscripts

Could anyone tell me how I can index it so that I can call up say the jth row 
for the ith person?

As a secondary question, when using 
do.call("rbind", args) is it possible to use indexing i.e
do.call("rbind",
vector.list[[i,j]]) so that the vector from row j for each person are 
combined into a new matrix?

Many thanks for any help
Laura
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Bayesianbay at aol.com wrote:
> 
> Dear List
> 
> I am having a bit of a problem getting a program to work.
> 
> For each of i=1 to n persons I have a matrix (different for each person)
with
> m rows.
> 
> What I want to do, is create m new data sets such that the first is made up
> of the first row for each person from the original matrices, the second
> contains the second row for each person from the original matrices etc etc
up
> to the mth new set containing the mth row from the original matrices for
each
> person.
> 
> Say the original matrix for each person can be indexed by xfinal.list[[i]]
> 
> I want to extract for each person in turn, the jth row, i.e.
> xfinal.list[[i]][j,] then bind these n vectors into a new matrix.
> 
> I am a little confused as to how I can index the jth row from the ith
person,
> obviously I will need a loop
> 
> I thought I would be able to use something like:
> 
> for (j in 1:m) {
> for (i in 1:n) {
> vector.list[[i,j]]<-xfinal.list[[i]][j,]
> } }
Try:

  new.list <- vector(mode="list", length=m)
  for(j in 1:m){
    temp <- unlist(lapply(xfinal.list, function(x) x[j,])
    new.list[[j]] <- matrix(unlist(temp), nrow=n, byrow=TRUE)
  }
    
> However I get the error that [[]] is an improper number of subscripts
> 
> Could anyone tell me how I can index it so that I can call up say the jth
row
> for the ith person?
> 
> As a secondary question, when using
> do.call("rbind", args) is it possible to use indexing i.e
do.call("rbind",
> vector.list[[i,j]]) so that the vector from row j for each person are
> combined into a new matrix?
The double brackets are for list indexing - and that's one dimensional.
Two indexes are working for matrices/arrays in single brackets.

The do.call() explaination is left for its expert, Bill Venables.

Uwe Ligges
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(in the "body", not the subject !)  To: r-help-request at
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