How can dplyr::mutate() be used to add multiple columns to a single column, while using a vector to specify the column names to be combined?

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To add multiple columns to a single column while using a vector to specify the column names to be combined, we can use the across() function within mutate():

df <- df %>% 
  mutate(across(c(col1, col2, col3), ~ paste(col1, col2, col3)))

In this example, col1, col2, and col3 are the column names to be combined, specified using a vector. The across() function takes a vector of column names (c(col1, col2, col3)) and applies the specified function (~ paste(col1, col2, col3)) to each of those columns. In this case, the function pastes the values of col1, col2, and col3 together, separated by a space. The resulting column(s) will have the same name as the original column(s) but with the added suffix _new.