问题
I have a data frame with two columns that I am grouping by with dplyr
, a column of months (as numerics, e.g. 1 through 12), and several columns with statistical data following that (values unimportant). An example:
ID_1 ID_2 month st1 st2
1 1 1 0.5 0.2
1 1 2 0.7 0.9
1 1 3 1.1 1.7
1 1 4 2.6 0.8
1 1 5 1.8 1.3
1 1 6 2.1 2.2
1 1 7 0.5 0.2
1 1 8 0.7 0.9
1 1 9 1.1 1.7
1 1 10 2.6 0.8
1 1 11 1.8 1.3
1 1 12 2.1 2.2
1 2 1 0.5 0.2
1 2 2 0.7 0.9
1 2 3 1.1 1.7
1 2 4 2.6 0.8
1 2 5 1.8 1.3
1 2 6 2.1 2.2
1 2 7 0.5 0.2
1 2 9 1.1 1.7
1 2 10 2.6 0.8
1 2 11 1.8 1.3
1 2 12 2.1 2.2
For the second grouping (ID_1 = 1
and ID_2 = 2
), there is a month missing from the data (month = 8
). Is there a way I can find this month and insert a row with the correct ID_1
and ID_2
values, the missing month
value, and NA
values for the rest of the columns? I've been playing around with this using dplyr
functions and can't seem to figure it out, perhaps there is even a non-dplyr
solution out there as well.
PS: If it helps, each unique grouping of ID_1
and ID_2
will have no more than 1 month missing.
回答1:
This can be done via tidyr::complete
:
library(dplyr)
library(tidyr)
dat %>%
group_by(ID_1, ID_2) %>%
complete(month = 1:12)
Tail of dataset:
Source: local data frame [6 x 5]
Groups: ID_1, ID_2 [1]
ID_1 ID_2 month st1 st2
<int> <int> <int> <dbl> <dbl>
1 1 2 7 0.5 0.2
2 1 2 8 NA NA
3 1 2 9 1.1 1.7
4 1 2 10 2.6 0.8
5 1 2 11 1.8 1.3
6 1 2 12 2.1 2.2
回答2:
Expand grid to make all combos of groups, then merge:
# make reference with all needed rows
ref <- data.frame(expand.grid(unique(df1$ID_1),
unique(df1$ID_2),
1:12))
colnames(ref) <- colnames(df1)[1:3]
# them merge with all TRUE
res <- merge(df1, ref, all = TRUE)
# to check output, show only month = 8
res[ res$month == 8, ]
# ID_1 ID_2 month st1 st2
# 8 1 1 8 0.7 0.9
# 20 1 2 8 NA NA
回答3:
If you go with tidyr
, there is the complete
function for this, you can nest ID_1
and ID_2
if you want both of the two variables as your grouping variable:
library(tidyr)
df1 = df %>% complete(nesting(ID_1, ID_2), month)
tail(df1)
# Source: local data frame [6 x 5]
# ID_1 ID_2 month st1 st2
# <int> <int> <int> <dbl> <dbl>
# 1 1 2 7 0.5 0.2
# 2 1 2 8 NA NA
# 3 1 2 9 1.1 1.7
# 4 1 2 10 2.6 0.8
# 5 1 2 11 1.8 1.3
# 6 1 2 12 2.1 2.2
来源:https://stackoverflow.com/questions/39520558/find-missing-month-after-grouping-with-dplyr