Possible new features: subsetting time windows about incidence2 HOT 2 CLOSED

library(outbreaks)
library(incidence2)

dat <- ebola_sim_clean$linelist

inci <- incidence(
  dat,
  date_index = date_of_onset,
  interval = "1 week", 
  groups = gender
)

inci
#> An incidence2 object: 109 x 3
#> [5829 cases from days 2014-W15 to 2015-W18]
#> [interval: 1 week]
#> [cumulative: FALSE]
#> 
#>    date_index gender count
#>    <yrwk>     <fct>  <int>
#>  1 2014-W15   f          1
#>  2 2014-W16   m          1
#>  3 2014-W17   f          4
#>  4 2014-W17   m          1
#>  5 2014-W18   f          4
#>  6 2014-W19   f          9
#>  7 2014-W19   m          3
#>  8 2014-W20   f          7
#>  9 2014-W20   m         10
#> 10 2014-W21   f          8
#> # … with 99 more rows

keep_first(inci, 5)
#> An incidence2 object: 7 x 3
#> [23 cases from days 2014-W15 to 2014-W19]
#> [interval: 1 week]
#> [cumulative: FALSE]
#> 
#>   date_index gender count
#>   <yrwk>     <fct>  <int>
#> 1 2014-W15   f          1
#> 2 2014-W16   m          1
#> 3 2014-W17   f          4
#> 4 2014-W17   m          1
#> 5 2014-W18   f          4
#> 6 2014-W19   f          9
#> 7 2014-W19   m          3
keep_last(inci, 5)
#> An incidence2 object: 10 x 3
#> [199 cases from days 2015-W14 to 2015-W18]
#> [interval: 1 week]
#> [cumulative: FALSE]
#> 
#>    date_index gender count
#>    <yrwk>     <fct>  <int>
#>  1 2015-W14   f         29
#>  2 2015-W14   m         25
#>  3 2015-W15   f         18
#>  4 2015-W15   m         24
#>  5 2015-W16   f         26
#>  6 2015-W16   m         18
#>  7 2015-W17   f         18
#>  8 2015-W17   m         22
#>  9 2015-W18   f         10
#> 10 2015-W18   m          9