in R: Sum by group without summarising [duplicate]

问题

I have searched a lot, but not found a solution.

I have the following data frame:

 Age no.observations Factor
1    1               4      A
2    1               3      A
3    1              12      A
4    1               5      B
5    1               9      B
6    1               3      B
7    2              12      A
8    2               3      A
9    2               6      A
10   2               7      B
11   2               9      B
12   2               1      B

I would like to sum create another column with the sum by the categories Age and Factor, thus having 19 for the first three rows, 26 for the next three etc. I want this to be a column added to this data.frame, therefore dplyr and its summarise function do not help.

回答1:

Use mutate with group_by to not summarise:

df %>%
  group_by(Age, Factor) %>%
  mutate(no.observations.in.group = sum(no.observations)) %>%
  ungroup()

来源：https://stackoverflow.com/questions/39594279/in-r-sum-by-group-without-summarising

标签

sum