How to extend calendar periods to complete a dataframe in R?

Question

The code posted at the bottom does a nice job of filling in a dataframe, using package tidyr, so that all ID's end up with the same number of periods, in the case of period defined as number of months ("Period_1" in the below code). Base dataframe testDF has ID of 1 with 5 periods, and ID of 50 and 60 with only 3 periods each. The tidyr code creates additional periods ("Period_1") for ID of 50 and 60 so they too have 5 Period_1´s. The code copies down the "Bal" and "State" fields so that all ID end up with the same number of Period_1, which is correct.

However, how would I extend the calendar month expression of "Period_2" in the same manner, as illustrated immediately below?

Code:

library(tidyr)

testDF <-
  data.frame(
    ID = as.numeric(c(rep(1,5),rep(50,3),rep(60,3))),
    Period_1 = as.numeric(c(1:5,1:3,1:3)),
    Period_2 = c("2012-06","2012-07","2012-08","2012-09","2012-10","2013-06","2013-07","2013-08","2012-01","2012-02","2012-03"),
    Bal = as.numeric(c(rep(10,5),21:23,36:34)),
    State = c("XX","AA","BB","CC","XX","AA","BB","CC","SS","XX","AA")
  )

testDFextend <-
  testDF %>%
  tidyr::complete(ID, nesting(Period_1)) %>%
  tidyr::fill(Bal, State, .direction = "down")

testDFextend

Edit: rolling from one year to the next

A better OP example would have Period 2 = c("2012-06","2012-07","2012-08","2012-09","2012-10","2013-06","2013-07","2013-08","2012-10","2012-11","2012-12"), providing an example whereby extending Period_2 causes a rollover to the next year. Below I add to the tidyr/dplyr answer below to correctly roll over the year:

library(tidyr)
library(dplyr)

testDF <-
  data.frame(
    ID = as.numeric(c(rep(1,5),rep(50,3),rep(60,3))),
    Period_1 = as.numeric(c(1:5,1:3,1:3)),
    Period_2 = c("2012-06","2012-07","2012-08","2012-09","2012-10","2013-06","2013-07","2013-08","2012-10","2012-11","2012-12"),
    Bal = as.numeric(c(rep(10,5),21:23,36:34)),
    State = c("XX","AA","BB","CC","XX","AA","BB","CC","SS","XX","AA")
  )

testDFextend <-
  testDF %>%
  tidyr::complete(ID, nesting(Period_1)) %>%
  tidyr::fill(Bal, State, .direction = "down")

testDFextend %>% 
  separate(Period_2, into = c("year", "month"), convert = TRUE) %>% 
  fill(year) %>% 
  group_by(ID) %>% 
  mutate(month = sprintf("%02d", zoo::na.spline(month))) %>% 
  unite("Period_2", year, month, sep = "-") %>% 
# Now I add the below lines:
  separate(Period_2, into = c("year", "month"), convert = TRUE) %>% 
  mutate(month = as.integer(sprintf("%02d", zoo::na.spline(month)))) %>%
  mutate(year1 = ifelse(month > 12, year+trunc(month/12), year)) %>%
  mutate(month1 = ifelse(month > 12 & month%%12!= 0, month%%12, month)) %>%
  mutate(month1 = ifelse(month1 < 10, paste0(0,month1),month1)) %>%
  unite("Period_2", year1, month1, sep = "-") %>%
  select("ID","Period_1","Period_2","Bal","State")

Answer 1

A tidyverse solution based on zoo::na.spline. Note that it does not handle year changes. It's harder than I thought, especially because zoo::na.spline does not seem to work on yearmon format.

library(tidyr)
library(dplyr)
testDFextend %>% 
  separate(Period_2, into = c("year", "month"), convert = TRUE) %>% 
  fill(year) %>% 
  group_by(ID) %>% 
  mutate(month = sprintf("%02d", zoo::na.spline(month))) %>% 
  unite("Period_2", year, month, sep = "-")

output

      ID Period_1 Period_2   Bal State
   <dbl>    <dbl> <chr>    <dbl> <chr>
 1     1        1 2012-06     10 XX   
 2     1        2 2012-07     10 AA   
 3     1        3 2012-08     10 BB   
 4     1        4 2012-09     10 CC   
 5     1        5 2012-10     10 XX   
 6    50        1 2013-06     21 AA   
 7    50        2 2013-07     22 BB   
 8    50        3 2013-08     23 CC   
 9    50        4 2013-09     23 CC   
10    50        5 2013-10     23 CC   
11    60        1 2012-01     36 SS   
12    60        2 2012-02     35 XX   
13    60        3 2012-03     34 AA   
14    60        4 2012-04     34 AA   
15    60        5 2012-05     34 AA