[R] reading in file with different row length

[Muhammad Rahiz]

Hi all,

I have a file, say, test.txt, which contains the following information. 
I'm trying to read in the file and specifying the missing values as NA 
so that each column has the same number of rows.

I've tried all sorts of manipulation but to no avail.

r1 r2 r3
1   3
2   3
3 2 3
4 2 3
5 2 3
6 2 3
7 2
8 2
9 2 3

The output should be

r1 r2 r3
1 NA 3
2 NA 3
3 2 3
4 2 3
5 2 3
6 2 3
7 2 NA
8 2 NA
9 2 3

Muhammad