Summarize columns as new columns in a dataframe

Question

I have a dataframe df_workingFile:

group  | value
 a     |   1
 a     |   3
 b     |   2
 b     |   2

I want to add two new columns - one for the min and max for each group

group  | value | max | min
 a     |   1   |  3  |  1
 a     |   3   |  3  |  1
 b     |   2   |  2  |  2
 b     |   2   |  2  |  2

Right now I'm looping through each row and taking the min/max of the group's subset of data, but that's really slow with large datasets. What's an efficient way of doing this?

Answer 1

With the dplyr package you can do the following:

df_workingFile %>% 
  group_by(group) %>% 
  mutate(max = max(value), min = min(value)) %>% ungroup()

  # A tibble: 4 x 4
   group value   min   max
   <chr> <dbl> <dbl> <dbl>
1      a     1     1     3
2      a     3     1     3
3      b     2     2     2
4      b     2     2     2