Fuzzy Matching to data sets based on a Date

date_match_example.R

library(lubridate)

rdate <- function(size,
                  min = paste0(format(Sys.Date(), '%Y'), '-01-01'),
                  max = paste0(format(Sys.Date(), '%Y'), '-12-31'),
                  sort = TRUE) {
  
  dates <- sample(
    seq(as.Date(min), as.Date(max), by = "day"),
    size = size, replace = TRUE)
  if (sort == TRUE) {
    sort(dates)
  } else {
    dates
  }
  
}


id_vec = sample(letters[1:5], 100, replace = TRUE)
df = data.frame( date = rdate(100), id = id_vec)
df_2 = data.frame( date2 = rdate(100), id = id_vec, ind = 1:100)

library(dplyr)
# join all combos
oj = full_join(df, df_2, by = "id")
# just resort the data
oj = oj %>% 
  arrange(id, date, date2)
# get absolute difference in date
oj = oj %>% 
  mutate(date_diff = abs(date - date2))

# for each id/date pair, give the difference and the index for that
# difference 
oj_print = oj %>% 
  group_by(id, date) %>% 
  mutate( min_diff = min(date_diff), 
          index = ind[which.min(date_diff)])

# actually keep the closest
oj = oj %>% 
  group_by(id, date) %>% 
  slice(which.min(date_diff))