R - Fill missing dates by group

Question

In my data, there exist observations for some IDs in some months and not for others, e.g.

dat <- data.frame(c(1, 1, 1, 2, 3, 3, 3, 4, 4, 4), c(rep(30, 2),         


        

Answer 1

tidyr::complete() works given your example data:

library(tidyverse)
dat %>% 
  group_by(id) %>% 
  complete(date) %>% 
  ungroup()

      id date       value
          
 1  1.00 2017-01-01  30.0
 2  1.00 2017-02-01  30.0
 3  1.00 2017-03-01  NA  
 4  1.00 2017-04-01  25.0
 5  2.00 2017-01-01  NA  
 6  2.00 2017-02-01  25.0
 7  2.00 2017-03-01  NA  
 8  2.00 2017-04-01  NA  
 9  3.00 2017-01-01  25.0
10  3.00 2017-02-01  25.0
11  3.00 2017-03-01  25.0
12  3.00 2017-04-01  NA  
13  4.00 2017-01-01  20.0
14  4.00 2017-02-01  20.0
15  4.00 2017-03-01  NA  
16  4.00 2017-04-01  20.0