These functions determine which items in a vector can be considered (the start of) a new episode, based on the argument episode_days. This can be used to determine clinical episodes for any epidemiological analysis. The get_episode() function returns the index number of the episode per group, while the is_new_episode() function returns TRUE for every new get_episode() index, and is thus equal to !duplicated(get_episode(...)).
Arguments
- x
vector of dates (class
DateorPOSIXt), will be sorted internally to determine episodes- episode_days
required episode length in days, can also be less than a day or
Inf, see Details- ...
ignored, only in place to allow future extensions
Details
The functions get_episode() and is_new_episode() differ in this way when setting episode_days to 365:
| person_id | date | get_episode() | is_new_episode() |
| A | 2019-01-01 | 1 | TRUE |
| A | 2019-03-01 | 1 | FALSE |
| A | 2021-01-01 | 2 | TRUE |
| B | 2008-01-01 | 1 | TRUE |
| B | 2008-01-01 | 1 | FALSE |
| C | 2020-01-01 | 1 | TRUE |
Dates are first sorted from old to new. The oldest date will mark the start of the first episode. After this date, the next date will be marked that is at least episode_days days later than the start of the first episode. From that second marked date on, the next date will be marked that is at least episode_days days later than the start of the second episode which will be the start of the third episode, and so on. Before the vector is being returned, the original order will be restored.
The first_isolate() function is a wrapper around the is_new_episode() function, but is more efficient for data sets containing microorganism codes or names and allows for different isolate selection methods.
The dplyr package is not required for these functions to work, but these episode functions do support variable grouping and work conveniently inside dplyr verbs such as filter(), mutate() and summarise().
Examples
# `example_isolates` is a data set available in the AMR package.
# See ?example_isolates
df <- example_isolates[sample(seq_len(2000), size = 100), ]
get_episode(df$date, episode_days = 60) # indices
#> [1] 35 39 19 14 29 40 12 13 44 38 37 39 6 44 32 2 39 21 30 12 10 18 11 15 8
#> [26] 29 46 20 37 38 38 1 40 21 41 5 15 33 8 15 11 29 31 44 35 28 45 25 45 22
#> [51] 35 12 24 10 4 12 1 27 9 36 8 16 7 23 21 18 45 47 5 6 36 46 43 41 34
#> [76] 3 11 27 34 17 17 26 46 42 46 19 29 42 33 47 1 41 33 7 46 23 24 11 38 30
is_new_episode(df$date, episode_days = 60) # TRUE/FALSE
#> [1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE FALSE
#> [13] TRUE FALSE TRUE TRUE FALSE TRUE TRUE FALSE TRUE TRUE TRUE TRUE
#> [25] TRUE FALSE TRUE TRUE FALSE FALSE FALSE TRUE FALSE FALSE TRUE TRUE
#> [37] FALSE TRUE FALSE FALSE FALSE FALSE TRUE FALSE FALSE TRUE TRUE TRUE
#> [49] FALSE TRUE FALSE FALSE TRUE FALSE TRUE FALSE FALSE TRUE TRUE TRUE
#> [61] FALSE TRUE TRUE TRUE FALSE FALSE FALSE TRUE FALSE FALSE FALSE FALSE
#> [73] TRUE FALSE TRUE TRUE FALSE FALSE FALSE TRUE FALSE TRUE FALSE TRUE
#> [85] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
#> [97] FALSE FALSE FALSE FALSE
# filter on results from the third 60-day episode only, using base R
df[which(get_episode(df$date, 60) == 3), ]
#> # A tibble: 1 × 46
#> date patient age gender ward mo PEN OXA FLC AMX
#> <date> <chr> <dbl> <chr> <chr> <mo> <sir> <sir> <sir> <sir>
#> 1 2002-08-28 390178 57 M Clinical B_STRPT_SLVR S NA NA S
#> # … with 36 more variables: AMC <sir>, AMP <sir>, TZP <sir>, CZO <sir>,
#> # FEP <sir>, CXM <sir>, FOX <sir>, CTX <sir>, CAZ <sir>, CRO <sir>,
#> # GEN <sir>, TOB <sir>, AMK <sir>, KAN <sir>, TMP <sir>, SXT <sir>,
#> # NIT <sir>, FOS <sir>, LNZ <sir>, CIP <sir>, MFX <sir>, VAN <sir>,
#> # TEC <sir>, TCY <sir>, TGC <sir>, DOX <sir>, ERY <sir>, CLI <sir>,
#> # AZM <sir>, IPM <sir>, MEM <sir>, MTR <sir>, CHL <sir>, COL <sir>,
#> # MUP <sir>, RIF <sir>
# the functions also work for less than a day, e.g. to include one per hour:
get_episode(
c(
Sys.time(),
Sys.time() + 60 * 60
),
episode_days = 1 / 24
)
#> [1] 1 2
# \donttest{
if (require("dplyr")) {
# is_new_episode() can also be used in dplyr verbs to determine patient
# episodes based on any (combination of) grouping variables:
df %>%
mutate(condition = sample(
x = c("A", "B", "C"),
size = 100,
replace = TRUE
)) %>%
group_by(patient, condition) %>%
mutate(new_episode = is_new_episode(date, 365)) %>%
select(patient, date, condition, new_episode) %>%
arrange(patient, condition, date)
}
#> # A tibble: 100 × 4
#> # Groups: patient, condition [99]
#> patient date condition new_episode
#> <chr> <date> <chr> <lgl>
#> 1 0C0688 2014-09-05 B TRUE
#> 2 0DBF93 2015-12-03 A TRUE
#> 3 116866 2011-11-07 B TRUE
#> 4 15D386 2004-08-01 A TRUE
#> 5 174209 2011-10-03 B TRUE
#> 6 183220 2008-11-14 C TRUE
#> 7 202577 2011-06-18 C TRUE
#> 8 2FC253 2003-11-04 B TRUE
#> 9 304508 2004-05-09 A TRUE
#> 10 314039 2008-04-28 C TRUE
#> # … with 90 more rows
if (require("dplyr")) {
df %>%
group_by(ward, patient) %>%
transmute(date,
patient,
new_index = get_episode(date, 60),
new_logical = is_new_episode(date, 60)
) %>%
arrange(patient, ward, date)
}
#> # A tibble: 100 × 5
#> # Groups: ward, patient [94]
#> ward date patient new_index new_logical
#> <chr> <date> <chr> <int> <lgl>
#> 1 Clinical 2014-09-05 0C0688 1 TRUE
#> 2 ICU 2015-12-03 0DBF93 1 TRUE
#> 3 Clinical 2011-11-07 116866 1 TRUE
#> 4 ICU 2004-08-01 15D386 1 TRUE
#> 5 Outpatient 2011-10-03 174209 1 TRUE
#> 6 Clinical 2008-11-14 183220 1 TRUE
#> 7 ICU 2011-06-18 202577 1 TRUE
#> 8 ICU 2003-11-04 2FC253 1 TRUE
#> 9 Clinical 2004-05-09 304508 1 TRUE
#> 10 Clinical 2008-04-28 314039 1 TRUE
#> # … with 90 more rows
if (require("dplyr")) {
df %>%
group_by(ward) %>%
summarise(
n_patients = n_distinct(patient),
n_episodes_365 = sum(is_new_episode(date, episode_days = 365)),
n_episodes_60 = sum(is_new_episode(date, episode_days = 60)),
n_episodes_30 = sum(is_new_episode(date, episode_days = 30))
)
}
#> # A tibble: 3 × 5
#> ward n_patients n_episodes_365 n_episodes_60 n_episodes_30
#> <chr> <int> <int> <int> <int>
#> 1 Clinical 59 13 36 43
#> 2 ICU 31 10 24 27
#> 3 Outpatient 4 3 4 4
# grouping on patients and microorganisms leads to the same
# results as first_isolate() when using 'episode-based':
if (require("dplyr")) {
x <- df %>%
filter_first_isolate(
include_unknown = TRUE,
method = "episode-based"
)
y <- df %>%
group_by(patient, mo) %>%
filter(is_new_episode(date, 365)) %>%
ungroup()
identical(x, y)
}
#> [1] TRUE
# but is_new_episode() has a lot more flexibility than first_isolate(),
# since you can now group on anything that seems relevant:
if (require("dplyr")) {
df %>%
group_by(patient, mo, ward) %>%
mutate(flag_episode = is_new_episode(date, 365)) %>%
select(group_vars(.), flag_episode)
}
#> # A tibble: 100 × 4
#> # Groups: patient, mo, ward [96]
#> patient mo ward flag_episode
#> <chr> <mo> <chr> <lgl>
#> 1 789292 B_STRPT_GRPC Clinical TRUE
#> 2 534091 B_ESCHR_COLI Clinical TRUE
#> 3 F50462 B_STPHY_CONS ICU TRUE
#> 4 C89738 B_STPHY_CONS Clinical TRUE
#> 5 174209 B_STPHY_AURS Outpatient TRUE
#> 6 A84726 B_STPHY_HMNS ICU TRUE
#> 7 9B6789 B_STPHY_HMNS ICU TRUE
#> 8 E19253 B_STPHY_CONS Clinical TRUE
#> 9 D08278 B_ESCHR_COLI ICU TRUE
#> 10 C34429 B_PROTS_MRBL Clinical TRUE
#> # … with 90 more rows
# }