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rsummultiple-columns
Luke Bridgman
Luke Bridgman

Reputation: 3

Summing values in two different columns in R

I have a dataset in which I wish to sum each value in column n, with its corresponding value in column (n+(ncol/2)); i.e., so I can sum a value in column 1 row 1 with a value in column 12 row 1, for a dataset with 22 columns, and repeat this until column 11 is summed with column 22. The solution needs to work for hundreds of rows.

How do I do this using R, while ignoring the column names?

Upvotes: 0

Views: 114

Answers (1)

Weihuang Wong
Weihuang Wong

Reputation: 13108

Suppose your data is

d <- setNames(as.data.frame(matrix(rnorm(100 * 22), nc = 22)), LETTERS[1:22])

You can do a simple matrix addition using numbers to select the columns:

output <- d[, 1:11] + d[, 12:22]

so, e.g.

all.equal(output[,1], d[,1] + d[,12])
# [1] TRUE

Upvotes: 1

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