R help - Apr 2005 - Storing vectors as vectors and iterating through them

Hi all,

I have a bunch of int vectors. Each vector holds a bunch of ints that 
correspond to row numbers of an existing matrix. I use the int vectors to 
pull out rows of data from a matrix, i.e.

data <- my_matrix[int_vector,]

I would like to store these int vectors in some sort of data structure that 
will preserve them as-is and allow iteration. I guess what I'm looking for 
would be something analogous to the java Vector class, as in this java-like 
pseudocode :

Vector V = new Vector;
V.add(a,b,c) // where a,b,c are lists

for(int i = 0; i<V.size; i++)
{
    List L = (List)Vector.get(i);
    plot(L);
}

The point is to iterate through the data structure containing the int 
vectors, and, for each int vector, do some clustering and plotting, but what 
I cannot find is a data structure in R that would support this.. trying 
c(a,b,c) does not preserve each int vector, but instead merges all the ints 
into one vector. I need to keep them separate (so I can create a separate 
plot for each vector).

Thanks in advance,
Ken

Ken -- try using lists:
> vec.list <- list(1:5, 2:4, 3:8)
> vec.list <- c(vec.list, list(7:9))
> vec.list
[[1]]
[1] 1 2 3 4 5

[[2]]
[1] 2 3 4

[[3]]
[1] 3 4 5 6 7 8

[[4]]
[1] 7 8 9

Then you can use "lapply" or "sapply", or just a
"for" loop, to iterate over
the list, applying your function to each element.

Hope this helps,

Matt Wiener

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Ken Termiso
Sent: Monday, April 18, 2005 1:09 PM
To: r-help at stat.math.ethz.ch
Subject: [R] Storing vectors as vectors and iterating through them


Hi all,

I have a bunch of int vectors. Each vector holds a bunch of ints that 
correspond to row numbers of an existing matrix. I use the int vectors to 
pull out rows of data from a matrix, i.e.

data <- my_matrix[int_vector,]

I would like to store these int vectors in some sort of data structure that 
will preserve them as-is and allow iteration. I guess what I'm looking for 
would be something analogous to the java Vector class, as in this java-like 
pseudocode :

Vector V = new Vector;
V.add(a,b,c) // where a,b,c are lists

for(int i = 0; i<V.size; i++)
{
    List L = (List)Vector.get(i);
    plot(L);
}

The point is to iterate through the data structure containing the int 
vectors, and, for each int vector, do some clustering and plotting, but what

I cannot find is a data structure in R that would support this.. trying 
c(a,b,c) does not preserve each int vector, but instead merges all the ints 
into one vector. I need to keep them separate (so I can create a separate 
plot for each vector).

Thanks in advance,
Ken

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