Using dplyr to summarise multiple columns

Question

df <- data.frame(
    a = sample(1:5, n, replace = TRUE), 
    b = sample(1:5, n, replace = TRUE), 
    c = sample(1:5, n, replace = TRUE), 
    d = sample(1:5, n, replace = TRUE), 
    grp = sample(1:3, n, replace = TRUE)
)

There are three columns and one grouping variable in this data-set. I would want to calculate mean for each column within each group using dplyr

Answer 1

You can use the "sumamrise_all()" function for this purpose:

df %>% group_by(grp) %>% summarise_all(funs(mean))