How to calculate the sum of specific columns in R and make the results in a another column

Question

I'm a beginner in biostatistics and R software, and I need your help in a issue, I have a table that contains more than 170 columns and more than 6000 lines, I want to add another column that contains the sum of all the columns, except the columns one and two columns

so for example if I have the data of 5 columns from A to E

A     B     C     D    E
12   2     13    98    6
10   7      8    67  12
12   56    67    9    7

I want to add another column (Column F for example ) that contain the sum of columns C D and E ( that means all the columns except the first two columns

so the result will be

A     B     C     D      E        F
AA    2     13    98     6        117
CF    7      8    67     12       87
QZ    56    67    9      7        83

Please tell me if you want to know any other informations or clarification Thank you very much

Answer 1

Does this work:

library(dplyr)
df %>% rowwise() %>% mutate(F = sum(c_across(-c(A:B))))
# A tibble: 3 x 6
# Rowwise: 
      A     B     C     D     E     F
  <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
1    12     2    13    98     6   117
2    10     7     8    67    12    87
3    12    56    67     9     7    83

Data used:

df
# A tibble: 3 x 5
      A     B     C     D     E
  <dbl> <dbl> <dbl> <dbl> <dbl>
1    12     2    13    98     6
2    10     7     8    67    12
3    12    56    67     9     7

Answer 2

library(tibble)
library(dplyr)

tbl <-
tibble::tribble(
  ~A, ~B, ~C, ~D, ~E,
  12, 2, 13,  98,  6,
  10, 7, 8,   67,  12,
  12, 56, 67,  9,  7
)


tbl %>% dplyr::mutate("F" =  C + D + E )
## R might consider F to be abbreviation for FALSE, so i put it in ""

Answer 3

You will find the information you need in the top answer to this question:

stackoverflow.com/questions/3991905/sum-rows-in-data-frame-or-matrix

Basically, you just name your new column, use the rowSums function, and specify the columns you want to include with the square bracket subsetting.

data$new <- rowSums( data[,43:167] )