tidier

set.seed(101)
airquality |>
  # create date column
  dplyr::mutate(date_col = lubridate::make_date(1973, Month, Day)) |>
  # create gaps by removing some days
  dplyr::slice_sample(prop = 0.8) |> 
  # compute mean temperature over last seven days in the same month
  tidier::mutate(avg_temp_over_last_week = mean(Temp, na.rm = TRUE),
                 .order_by = date_col,
                 .by       = Month,
                 .frame    = range_between(lubridate::days(7), # 7 days before current row
                                           lubridate::days(-1) # do not include current row
                                           )
                 )
#> # A tibble: 122 × 8
#>    Ozone Solar.R  Wind  Temp Month   Day date_col   avg_temp_over_last_week
#>    <int>   <int> <dbl> <int> <int> <int> <date>                       <dbl>
#>  1    10     264  14.3    73     7    12 1973-07-12                    85.5
#>  2    NA     127   8      78     6    26 1973-06-26                    75.4
#>  3    16      77   7.4    82     8     3 1973-08-03                    81  
#>  4    14     191  14.3    75     9    28 1973-09-28                    71.8
#>  5    NA     138   8      83     6    30 1973-06-30                    76.6
#>  6    NA      98  11.5    80     6    28 1973-06-28                    75.8
#>  7   122     255   4      89     8     7 1973-08-07                    83.7
#>  8    47      95   7.4    87     9     5 1973-09-05                    92.5
#>  9    23     220  10.3    78     9     8 1973-09-08                    90.7
#> 10    NA     286   8.6    78     6     1 1973-06-01                   NaN  
#> # ℹ 112 more rows