Season week
Season week is the week number within an epidemiological season. It is used for surveillance outcomes such as influenza, where aligning data to a season rather than a calendar year makes trends easier to compare across years.
Isoweek runs from 1 to 53; season week runs from 1 to 52. When isoweek is 53, the corresponding season week is 18.5.
library(cstime)
library(magrittr)
library(data.table)
#>
#> Attaching package: 'data.table'
#> The following object is masked from 'package:base':
#>
#> %notin%Mapping between isoweek and season week
The chart below shows the relationship across all isoweek values, with the special case of isoweek 53 highlighted.
Conversion functions
seasonweek_to_isoweek_c(10)
#> [1] "44"
seasonweek_to_isoweek_n(10)
#> [1] 44
isoweek_to_seasonweek_n(1)
#> [1] 19
seasonweek_to_isoweek_n(1:52)
#> [1] 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 1 2 3 4 5 6 7
#> [26] 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
#> [51] 33 34
isoweek_to_seasonweek_n(1:53)
#> [1] 19.0 20.0 21.0 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29.0 30.0 31.0 32.0 33.0
#> [16] 34.0 35.0 36.0 37.0 38.0 39.0 40.0 41.0 42.0 43.0 44.0 45.0 46.0 47.0 48.0
#> [31] 49.0 50.0 51.0 52.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0
#> [46] 12.0 13.0 14.0 15.0 16.0 17.0 18.0 18.5