Tidyr::fill example

tidyr_fill.r

# generate dataset with 1x year per every 12 months
df <- data.frame(Month = rep(1:12, 3), 
                 Year = c(2000, rep(NA, 11), 
                          2001, rep(NA, 11), 
                          2002, rep(NA, 11)))

# view the funky dataset
df

# fill the dataset with missing year!
# and bask in the glory of the clean datset!

df %>% 
    fill(Year)