# Calculating specific columns across rows

I feel like this is a very simple question, I just can't figure it out. I have a dataset with about 60 rows and 40 columns. I would like to take a few columns and sum them according to each row to create a new column. What is the command for this?

Can you provide a reproducible example?

Otherwise, something like this using `mtcars` to get the sum for all of the columns that contain an 'a' in the name.

``````library(dplyr)
mtcars |>
rowwise() |>
mutate(test = sum(across(contains("a")))) |>
ungroup()
``````

`test` = drat + am + gear + carb

``````# A tibble: 32 x 12
mpg   cyl  disp    hp  drat    wt  qsec    vs    am  gear  carb  test
<dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
1  21       6  160    110  3.9   2.62  16.5     0     1     4     4 12.9
2  21       6  160    110  3.9   2.88  17.0     0     1     4     4 12.9
3  22.8     4  108     93  3.85  2.32  18.6     1     1     4     1  9.85
4  21.4     6  258    110  3.08  3.22  19.4     1     0     3     1  7.08
5  18.7     8  360    175  3.15  3.44  17.0     0     0     3     2  8.15
6  18.1     6  225    105  2.76  3.46  20.2     1     0     3     1  6.76
7  14.3     8  360    245  3.21  3.57  15.8     0     0     3     4 10.2
8  24.4     4  147.    62  3.69  3.19  20       1     0     4     2  9.69
9  22.8     4  141.    95  3.92  3.15  22.9     1     0     4     2  9.92
10  19.2     6  168.   123  3.92  3.44  18.3     1     0     4     4 11.9
# i 22 more rows
# i Use `print(n = ...)` to see more rows
``````