I need Column sum as sum12 is sum of 1st columns and sum34 is of column 3 and 4

Question

col1 col2   col3    col4
1     4        1    4
2     4        2    5
4     5        3    6
5     6        5    7

I need column sum like

col1    col2    col3    col4    sum12   sum34
1         4       1       4       5       5
2         4       2       5       6       7
4         5       3       6       9       9
5         6       5       7       11      12

Answer 1

We can use transform

transform(df, sum12 = col1 + col2, sum34 = col3 + col4)

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Or another option is

df[c("sum12", "sum34")] <- df[c(1,3)] + df[c(2,4)]
df
#   col1 col2 col3 col4 sum12 sum34
#1    1    4    1    4     5     5
#2    2    4    2    5     6     7
#3    4    5    3    6     9     9
#4    5    6    5    7    11    12