user1807857 user1807857 - 2 months ago 13
R Question

sum cells of certain columns for each row

I would like to calculate sums for certain colums and then apply this summation for every row.
Unfortunately, I can only get to the first step. How do I now make it happen for each row?
I know that R doesn't need loops but what would be the correct approach?

My matrix (zscore) looks like this:

a b c t y
1 3 4 7 7 4

2 4 56 6 6 4

3 3 3 2 1 7

4 3 88 9 9 9


Now I would want to calculate the row sum for each row, based on some of the colums. For one row it could look like this:

f1 <- sum(zscore[1,1:2], zscore[1,3], zscore[1,5])


How do I do that now for each row?

Answer

You could do something like this:

summed <- rowSums(zscore[, c(1, 2, 3, 5)])