[R] :How to insert a column in a data frame

[Rolf Turner]

On 18/02/2009, at 12:51 PM, Laura Rodriguez Murillo wrote:

> Hi dear list,
>
> I wonder if somebody can help me with this. I have a text file with
> 300 rows and around 300000 columns and I need to insert a column that
> has the number 1 in every row. This new column should be placed
> between columns 6 and 7.
>
> As an example: I would want to insert a column (consiting just of the
> number 1 in every row, as in column 6) between columns 6 and 7.
>
> 847 847 0 0 2 1 G G T C A G T T C G A C C C G C A A A G G G G A C A  
> T T
> 847 847 0 0 2 1 G G T C A G T T C G A C C C G C A A A G G G G A C A  
> T T
> 847 847 0 0 2 1 G G T C A G T T C G A C C C G C A A A G G G G A C A  
> T T
> 847 847 0 0 2 1 G G T C A G T T C G A C C C G C A A A G G G G A C A  
> T T
> 847 847 0 0 2 1 G G T C A G T T C G A C C C G C A A A G G G G A C A  
> T T
> 847 847 0 0 2 1 G G T C A G T T C G A C C C G C A A A G G G G A C A  
> T T
>
> So the new table would look like this:
>
> 847 847 0 0 2 1 1 G G T C A G T T C G A C C C G C A A A G G G G A C  
> A T T
> 847 847 0 0 2 1 1 G G T C A G T T C G A C C C G C A A A G G G G A C  
> A T T
> 847 847 0 0 2 1 1 G G T C A G T T C G A C C C G C A A A G G G G A C  
> A T T
> 847 847 0 0 2 1 1 G G T C A G T T C G A C C C G C A A A G G G G A C  
> A T T
> 847 847 0 0 2 1 1 G G T C A G T T C G A C C C G C A A A G G G G A C  
> A T T
> 847 847 0 0 2 1 1 G G T C A G T T C G A C C C G C A A A G G G G A C  
> A T T
>
> You can also look at this problem as duplicating column 6.

(1) y <- cbind(x[,1:6],clyde=rep(1,300),x[,7:ncol(x)])

(2) y <- as.data.frame(c(x[1:6],list(clyde=rep(1,300)),x[7:length(x)]))

where x is your original data stored as a matrix or data frame in  
method (1),
and as a data frame in method (2), and y is the new data set with the  
extra
column of 1's.

Or, if you really are just duplicating column 6:

	y <- x[,c(1:6,6,7:ncol(x))]
	names(y)[7] <- "clyde"        # For consistency with other methods.

These work with your toy example.  I haven't tried them out with data  
sets of
the size of your real data set.

	cheers,

		Rolf Turner

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