R dataframe: sum of certain rows into new column

Question

I have a dataframe in which I'd like to create a new column where each cell is formed by the sum of some other rows.

My dataframe would be like:

    Type    A    B    C
1     X     1    6    5
2     X     3    4    0
3     Y     4    1    0
4     Z     0    0    1

And my expected output:

    Type    A    B    C    D
1     X     1    6    5    12
2     X     3    4    0    7
3     Y     4    1    0    5
4     Z     0    0    1    1

I need to add the names of the columns I want to sum as a vector, such as c("A","B","C"), and I've tried functions such as rowSums and rowsum but they're not working properly.

`df$D <- rowSums(df[c("A","B","C")])` – Ronak Shah Feb 08 '21 at 10:52 — Ronak Shah, Feb 08 '21 at 10:52
is there a way to add them inside a `mutate` function? – MustardRecord Feb 08 '21 at 10:53 — MustardRecord, Feb 08 '21 at 10:53
`df %>% mutate(D = rowSums(select(., A, B, C)))` – Ronak Shah Feb 08 '21 at 10:54 — Ronak Shah, Feb 08 '21 at 10:54

score 2 · Accepted Answer · answered Feb 08 '21 at 10:55

2

A possible solution with dplyr:

df <- tribble(
~"A", ~"B", ~"C",
1, 6, 5,
3, 4, 0,
4, 1, 0,
0, 0, 1
)

df %>% 
  rowwise() %>% 
  mutate(D = sum(c_across(A:C)))

answered Feb 08 '21 at 10:55

Leonardo

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R dataframe: sum of certain rows into new column

1 Answers1