adding a New column and add the rows to the newly created column

Question

I have a 100x20 matrix now I want to add a new column and I have to do the sum of the twenty columns. I am trying to find a function to do this, can any one help

possible duplicate of [Vector that is sum of rows](http://stackoverflow.com/questions/3991905/vector-that-is-sum-of-rows) — Brian Diggs, Mar 10 '14 at 18:58

score 2 · Answer 1 · answered Feb 15 '14 at 06:55

2

You are looking for rowSums. if your data is m

m <- matrix(rexp(2000, rate=.1), ncol=20)
#creating totals
mtotal <- rowSums(m)
#adding totals to the matrix    
m <- cbind(m,mtotal)

answered Feb 15 '14 at 06:55

Rfan

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score 0 · Accepted Answer · edited May 23 '17 at 12:05

0

You want to add a new column to the matrix, with values that are the sum of the existing columns?

Given your matrix in m, this should do it:

newcol <- sapply(1:nrow(m), function(row) { sum(m[row,]) })
m <- cbind(m, newcol)

UPDATE

I didn't know rowSums! As @Rfan pointed out, this could be simplified to:

m <- cbind(m, rowSums(m))

edited May 23 '17 at 12:05

Community

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answered Feb 15 '14 at 06:47

janos

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adding a New column and add the rows to the newly created column

2 Answers2