Combining multiple data.frames using R

Question

I have several txt files in which each txt file contains 3 columns(A,B,C). Column A will be common to all txt files. Now I want to combine txt files with coulmn A appearing only once while the other columns (B and C) of respective files. I used cbind but it creates a data frame with repeats of column A, which I dont want. The column A must be repeated only once. Here is the R code I tried:

data <- read.delim(file.choose(),header=T)   
data2 <- read.delim(file.choose(),header=T)
data3 <- cbind(data1,data2)
write.table(data3,file="sample.txt",sep="\t",col.names=NA)

Ari B. Friedman · Accepted Answer · 2011-08-03 10:10:19Z

8

Unless your files are all sorted precisely the same, you'll need to use merge:

dat <- merge(data,data2,by="A")
dat <- merge(dat,data3,by="A")

This should automatically prevent you from having multiple A's, since merge knows they're all a key/index column. You'll likely want to rename the duplicate B's and C's before merging.

answered Aug 3, 2011 at 10:10

Ari B. Friedman

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Iterator Over a year ago

gsk3's solution is also better than cbind because it doesn't require assuming that the A values are identical matches. If, for instance, the A values (rows) are permuted, gsk3's solution will still give the right answer.

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