How to group by a fixed number of rows in dplyr?

Question

I have a data frame:

set.seed(123)
x <- sample(10)
y <- x^2
my.df <- data.frame(x, y)

The result is this:

> my.         


        

Answer 1

Another option could be:

my.df %>%
 group_by(x = ceiling(row_number()/5)) %>%
 summarise_all(list(sum = sum, mean = mean))

      x   sum  mean
    
1     1   174  34.8
2     2   211  42.2