R-how to add columns to a data frame in a for loop?

Question

I have data that looks like this and 1000 files with the same data format.

R_338   4
R_341   1
R_471   1
R_491   4
R_494   1
R_642   0
M_218   5
M_222   5
M_292   0
p_185   5
p_187   5
A_308   0
A_473   1

I would really appreciate if someone can direct me to as to how i can write a R script to so that i can merge all 1000 files by only keeping the first column once and the rest 0f the 1000 columns appended:

Example output:

R_338   4   5   6   7   8   9   10  11
R_341   1   1   1   1   1   1   1   1
R_471   1   1   0   1   1   1   2   1
R_491   4   4   4   4   4   4   2   0
R_494   1   1   1   1   1   1   1   1
R_642   0   1   0   9   1   1   2   1
M_218   5   5   5   9   5   5   5   9
M_222   5   5   5   5   5   5   5   5
M_292   0   5   1   1   1   1   1   1
p_185   5   5   5   6   5   5   5   5
p_187   5   9   5   5   5   5   3   5
A_308   0   4   4   4   2   4   4   4
A_473   1   1   1   1   0   1   1   0

It probably doesn't matter, but the second column 4,1,1,4,1,... in your example input has not been perfectly reproduced in the second column of your example output. — Henry
– Henry, Commented Jul 10, 2011 at 23:06
i did correct that.i did look at cbind but it is not adding columns to the final matrix...do you know the correct syntax... — RnD
– RnD, Commented Jul 10, 2011 at 23:14
it's not clear from your question whether the first "column" is really a separate column or whether it is the row names of an otherwise numeric data set ... — Ben Bolker
– Ben Bolker, Commented Jul 11, 2011 at 12:19

Ben Bolker · Accepted Answer · 2011-07-11 00:40:31Z

3

Suppose you have a character vector containing the file names. Then I think

L <- lapply(file.names,read.table,...)  ## where ... represents additional 
                                        ## arguments to read.table()
cbind(L[[1]],do.call(cbind,lapply(L[-1],"[[",2)))

might work.

answered Jul 11, 2011 at 0:40

Ben Bolker

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Henry · Accepted Answer · 2011-07-10 23:09:36Z

-1

It rather depends on the precise details of what you have, but cbind or merge are likely to provide you with what you need.

answered Jul 10, 2011 at 23:09

Henry

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