[R] simple loop questions

[xueke at pdx.edu]

Hi all,

I am trying to write a loop to return the matched index for a column  
of values. Here is an simple example of this,

A   B
0   5
1   2
2   2
3   4
4   1
5   4
6   2

In this case, A is an index column for B. Now I have this new column C  
with just two values of 2 and 4. I want to match column C with column  
B, and return the matched indexes. So what I desire is to return:

[1] 1 2 6
[2] 3 5

Since value 2 corresponds to indexes 1,2,6, and 4 corresponds to indexes 3,5.

Is there any way to write a loop to have this done? Thank you for the help.

Xueke