Summarize with dplyr “other then” groups

Question

I need to summarize in a grouped data_frame (warn: a solution with dplyr is very much appreciated but isn\'t mandatory) both something on each group (simple) and the same so

Answer 1

Here's my solution:

res <- df %>%
  group_by(group) %>%
  summarise(med_group = median(value),
            med_other = (median(df$value[df$group != group]))) %>% 
  mutate(med_before = lag(med_group))

> res
Source: local data frame [3 x 4]

      group med_group med_other med_before
  (chr)     (dbl)     (dbl)      (dbl)
1     a       1.5       4.5         NA
2     b       3.5       3.5        1.5
3     c       5.5       2.5        3.5

I was trying to come up with an all-dplyr solution but base R subsetting works just fine with median(df$value[df$group != group]) returning the median of all observations that are not in the current group.

I hope this help you to solve your problem.