[R] concatenate values of two columns

[Marshall Feldman]

On 5/5/2010 6:00 AM, n.vialma at libero.it wrote:
> Dear list,
> I'm trying to concatenate the values of two columns but im not able to do it:
>
> i have a dataframe with the following two columns:
>
> X               VAR1       VAR2
> 1                                   2
> 2                   1
> 3                   2
> 4                                   3
> 5                                   4
> 6                  4
>
>
> what i would like to obtain is:
> X               VAR3
> 1                   2
> 2                   1
> 3                   2
> 4                   3
> 5                  4
> 6                  4
>
> I try with paste but what I obtain is:
> X                 VAR3
>
> 1                   NA2
> 2                    1NA
>
> 3                    2NA
>
> 4                    NA3
>
> 5                    NA4
>
> 6                    4NA
>
>   Thanks a lot!!
>
> 	[[alternative HTML version deleted]]
>
>    

Hi,

You don't say what you want to do when both VAR1 and VAR2 have 
non-trivial values. Neither do you indicate what is in the cells that 
are blank in your example. Nonetheless, consider this code:

 > X <- data.frame()
 > X <- edit(X)
 > X
   VAR1 VAR2
1   NA    2
2    1   NA
3    2   NA
4   NA    3
5   NA    4
6    4   NA

 > VAR3 <- X$VAR1
 > VAR3
[1] NA  1  2 NA NA  4
 > VAR3[is.na(VAR3)] <- X$VAR2[!is.na(X$VAR2)]
 > VAR3
[1] 2 1 2 3 4 4
 > X <- cbind(X,VAR3)
 > X
   VAR1 VAR2 VAR3
1   NA    2    2
2    1   NA    1
3    2   NA    2
4   NA    3    3
5   NA    4    4
6    4   NA    4

Q.E.D.

     Marsh Feldman