r - filtering data.frame based on row_number()

Question

UPDATE: dplyr has been updated since this question was asked and now performs as the OP wanted

I′m trying to get the second to the seventh line in a data.frame using dplyr.

I′m doing this:

require(dplyr)
df <- data.frame(id = 1:10, var = runif(10))
df <- df %>% filter(row_number() <= 7, row_number() >= 2)

But this throws an error.

Error in rank(x, ties.method = "first") : 
  argument "x" is missing, with no default

I know i could easily make:

df <- df %>% mutate(rn = row_number()) %>% filter(rn <= 7, rn >= 2)

But I would like to understand why my first try is not working.

question from:https://stackoverflow.com/questions/25994307/filtering-data-frame-based-on-row-number

Answer 1

Actually dplyr's slice function is made for this kind of subsetting:

df %>% slice(2:7)

(I'm a little late to the party but thought I'd add this for future readers)