| Title: | Convert Dates to Arbitrary Week Definitions |
|---|---|
| Description: | Which day a week starts depends heavily on the either the local or professional context. This package is designed to be a lightweight solution to easily switching between week-based date definitions. |
| Authors: | Zhian N. Kamvar [aut, cre] |
| Maintainer: | Zhian N. Kamvar <[email protected]> |
| License: | MIT + file LICENSE |
| Version: | 1.0.2 |
| Built: | 2024-11-01 11:25:51 UTC |
| Source: | https://github.com/reconhub/aweek |
The aweek package is a lightweight solution for converting dates to weeks that can start on any weekday. It implements the aweek class, which can easily be converted to date and weeks that start on different days.
When you work with aweek, you will want to make sure that you set the default
week_start variable to indicate which day of the week your weeks should
begin. This can be done with set_week_start(). It will ensure that all of
your weeks will begin on the same day.
get_week_start() returns the global week_start option
set_week_start() sets the global week_start option
This conversion is the simplest because dates are unambiguous.
date2week() converts dates, datetimes, and characters that look like dates to weeks
as.aweek() is a wrapper around date2week() that converts dates and datetimes
If you have separate columns for week numbers and years, then this is the
option for you. This allows you to specify a different start for each week
element using the start argument.
get_aweek() converts week numbers (with years and days) to aweek objects.
get_date() converts week numbers (with years and days) to Dates.
as.aweek() converts ISO-week formatted strings to aweek objects.
week2date() converts ISO-week formatted strings to Date.
This conversion is simple for aweek objects since their week_start is unambiguous
as.POSIXlt() converts to POSIXlt.
You can strip the week_start attribute of the aweek object by converting to
a character with as.character()
trunc() removes the weekday element of the ISO week string.
factor_aweek() does the same thing as trunc(), but will create a factor
with levels spanning all the weeks from the first week to the last week.
Useful for creating tables with zero counts for unobserved weeks.
change_week_start() will change the week_start attribute and adjust the
weeks accordingly so that the dates will always be consistent.
When you combine aweek objects, they must have the same week_start attribute. Characters can be added to aweek objects as long as they are in ISO week format and you can safely assume that they start on the same weekday. Dates are trivial to add to aweek objects. See the aweek documentation for details.
Maintainer: Zhian N. Kamvar [email protected]
Useful links:
Report bugs at https://github.com/reconhub/aweek/issues/
# At the beginning of your analysis, set the week start to the weeks you want # to use for reporting ow <- set_week_start("Sunday") # convert dates to weeks d <- as.Date(c("2014-02-11", "2014-03-04")) w <- as.aweek(d) w # get the week numbers date2week(d, numeric = TRUE) # convert back to date as.Date(w) # convert to factor factor_aweek(w) # append a week w[3] <- as.Date("2014-10-31") w # change week start variable (if needed) change_week_start(w, "Monday") # note that the date remains the same as.Date(change_week_start(w, "Monday")) # Don't forget to reset the week_start at the end set_week_start(ow)# At the beginning of your analysis, set the week start to the weeks you want # to use for reporting ow <- set_week_start("Sunday") # convert dates to weeks d <- as.Date(c("2014-02-11", "2014-03-04")) w <- as.aweek(d) w # get the week numbers date2week(d, numeric = TRUE) # convert back to date as.Date(w) # convert to factor factor_aweek(w) # append a week w[3] <- as.Date("2014-10-31") w # change week start variable (if needed) change_week_start(w, "Monday") # note that the date remains the same as.Date(change_week_start(w, "Monday")) # Don't forget to reset the week_start at the end set_week_start(ow)
Convert characters or dates to aweek objects
as.aweek(x, week_start = get_week_start(), ...) ## Default S3 method: as.aweek(x, week_start = NULL, ...) ## S3 method for class ''NULL'' as.aweek(x, week_start = NULL, ...) ## S3 method for class 'character' as.aweek(x, week_start = get_week_start(), start = week_start, ...) ## S3 method for class 'factor' as.aweek(x, week_start = get_week_start(), ...) ## S3 method for class 'Date' as.aweek(x, week_start = get_week_start(), ...) ## S3 method for class 'POSIXt' as.aweek(x, week_start = get_week_start(), ...) ## S3 method for class 'aweek' as.aweek(x, week_start = NULL, ...)as.aweek(x, week_start = get_week_start(), ...) ## Default S3 method: as.aweek(x, week_start = NULL, ...) ## S3 method for class ''NULL'' as.aweek(x, week_start = NULL, ...) ## S3 method for class 'character' as.aweek(x, week_start = get_week_start(), start = week_start, ...) ## S3 method for class 'factor' as.aweek(x, week_start = get_week_start(), ...) ## S3 method for class 'Date' as.aweek(x, week_start = get_week_start(), ...) ## S3 method for class 'POSIXt' as.aweek(x, week_start = get_week_start(), ...) ## S3 method for class 'aweek' as.aweek(x, week_start = NULL, ...)
x |
a Date, POSIXct, POSIXlt, or a correctly formatted (YYYY-Www-d) character string that represents the year, week, and weekday. |
week_start |
a number indicating the start of the week based on the ISO
8601 standard from 1 to 7 where 1 = Monday OR an abbreviation of the
weekdate in an English or current locale. Note: using a non-English locale
may render your code non-portable. Defaults to the value of
|
... |
arguments passed on to |
start |
an integer (or character) vector of days that the weeks
start on for each corresponding week. Defaults to the value of
|
The as.aweek() will coerce character, dates, and datetime objects
to aweek objects. Dates are trivial to convert to weeks because there is
only one correct way to convert them with any given week_start.
There is a bit of nuance to be aware of when converting characters to aweek objects:
The characters must be correctly formatted as YYYY-Www-d, where YYYY
is the year relative to the week, Www is the week number (ww) prepended
by a W, and d (optional) is the day of the week from 1 to 7 where 1
represents the week_start. This means that characters formatted as
dates will be rejected.
By default, the week_start and start parameters are identical. If
your data contains heterogeneous weeks (e.g. some dates will have the
week start on Monday and some will have the week start on Sunday), then
you should use the start parameter to reflect this. Internally, the
weeks will first be converted to dates with their respective starts and
then converted back to weeks, unified under the week_start parameter.
an aweek object
factors are first converted to characters before they are converted to aweek objects.
"aweek-class" for details on the aweek object,
get_aweek() for converting numeric weeks to weeks or dates,
date2week() for converting dates to weeks, week2date() for converting
weeks to dates.
# aweek objects can only be created from valid weeks: as.aweek("2018-W10-5", week_start = 7) # works! try(as.aweek("2018-10-5", week_start = 7)) # doesn't work :( # you can also convert dates or datetimes as.aweek(Sys.Date()) as.aweek(Sys.time()) # all functions get passed to date2week, so you can use any of its arguments: as.aweek("2018-W10-5", week_start = 7, floor_day = TRUE, factor = TRUE) as.aweek(as.Date("2018-03-09"), floor_day = TRUE, factor = TRUE) # If you have a character vector where different elements begin on different # days of the week, you can use the "start" argument to ensure they are # correctly converted. as.aweek(c(mon = "2018-W10-1", tue = "2018-W10-1"), week_start = "Monday", start = c("Monday", "Tuesday")) # you can convert aweek objects to aweek objects: x <- get_aweek() as.aweek(x) as.aweek(x, week_start = 7)# aweek objects can only be created from valid weeks: as.aweek("2018-W10-5", week_start = 7) # works! try(as.aweek("2018-10-5", week_start = 7)) # doesn't work :( # you can also convert dates or datetimes as.aweek(Sys.Date()) as.aweek(Sys.time()) # all functions get passed to date2week, so you can use any of its arguments: as.aweek("2018-W10-5", week_start = 7, floor_day = TRUE, factor = TRUE) as.aweek(as.Date("2018-03-09"), floor_day = TRUE, factor = TRUE) # If you have a character vector where different elements begin on different # days of the week, you can use the "start" argument to ensure they are # correctly converted. as.aweek(c(mon = "2018-W10-1", tue = "2018-W10-1"), week_start = "Monday", start = c("Monday", "Tuesday")) # you can convert aweek objects to aweek objects: x <- get_aweek() as.aweek(x) as.aweek(x, week_start = 7)
Convert aweek objects to a data frame
## S3 method for class 'aweek' as.data.frame(x, ...)## S3 method for class 'aweek' as.data.frame(x, ...)
x |
an aweek object |
... |
unused |
a data frame with an aweek column
d <- as.Date("2019-03-25") + 0:6 w <- date2week(d, "Sunday") dw <- data.frame(date = d, week = w) dw dw$weekd <- as.Date("2019-03-25") + 0:6 w <- date2week(d, "Sunday") dw <- data.frame(date = d, week = w) dw dw$week
Convert aweek objects to characters or dates
## S3 method for class 'aweek' as.Date(x, floor_day = FALSE, ...) ## S3 method for class 'aweek' as.POSIXlt(x, tz = "", floor_day = FALSE, ...) ## S3 method for class 'aweek' as.character(x, ...)## S3 method for class 'aweek' as.Date(x, floor_day = FALSE, ...) ## S3 method for class 'aweek' as.POSIXlt(x, tz = "", floor_day = FALSE, ...) ## S3 method for class 'aweek' as.character(x, ...)
x |
an object of class aweek. |
floor_day |
when |
... |
parameters passed to |
tz |
passed on to |
w <- date2week(Sys.Date(), week_start = "Sunday") w # convert to POSIX as.POSIXlt(w) as.POSIXlt(w, floor_day = TRUE) as.POSIXlt(w, floor_day = TRUE, tz = "KST") # convert to date as.Date(w) as.Date(w, floor_day = TRUE) # convert to character (strip attributes) as.character(w)w <- date2week(Sys.Date(), week_start = "Sunday") w # convert to POSIX as.POSIXlt(w) as.POSIXlt(w, floor_day = TRUE) as.POSIXlt(w, floor_day = TRUE, tz = "KST") # convert to date as.Date(w) as.Date(w, floor_day = TRUE) # convert to character (strip attributes) as.character(w)
This will change the week_start attribute of an aweek object and adjust the observations accordingly.
change_week_start(x, week_start = NULL, ...)change_week_start(x, week_start = NULL, ...)
x |
a Date, POSIXt, character, or any data that can be easily
converted to a date with |
week_start |
a number indicating the start of the week based on the ISO
8601 standard from 1 to 7 where 1 = Monday OR an abbreviation of the
weekdate in an English or current locale. Note: using a non-English locale
may render your code non-portable. Unlike |
... |
arguments passed to |
get_week_start() for accessing the global and local week_start
attribute, as.aweek(), which wraps this function.
# New Year's 2019 is the third day of the week starting on a Sunday s <- date2week(as.Date("2019-01-01"), week_start = "Sunday") s # It's the second day of the week starting on a Monday m <- change_week_start(s, "Monday") m # When you compare the underlying dates, they are exactly the same identical(as.Date(s), as.Date(m)) # Since this will pass arguments to `date2week()`, you can modify other # aspects of the aweek object this way, but this is not advised. change_week_start(s, "Monday", floor_day = TRUE)# New Year's 2019 is the third day of the week starting on a Sunday s <- date2week(as.Date("2019-01-01"), week_start = "Sunday") s # It's the second day of the week starting on a Monday m <- change_week_start(s, "Monday") m # When you compare the underlying dates, they are exactly the same identical(as.Date(s), as.Date(m)) # Since this will pass arguments to `date2week()`, you can modify other # aspects of the aweek object this way, but this is not advised. change_week_start(s, "Monday", floor_day = TRUE)
Convert date to a an arbitrary week definition
date2week( x, week_start = get_week_start(), floor_day = factor, numeric = FALSE, factor = FALSE, ... ) week2date(x, week_start = get_week_start(), floor_day = FALSE)date2week( x, week_start = get_week_start(), floor_day = factor, numeric = FALSE, factor = FALSE, ... ) week2date(x, week_start = get_week_start(), floor_day = FALSE)
x |
a Date, POSIXt, character, or any data that can be easily
converted to a date with |
week_start |
a number indicating the start of the week based on the ISO
8601 standard from 1 to 7 where 1 = Monday OR an abbreviation of the
weekdate in an English or current locale. Note: using a non-English locale
may render your code non-portable. Defaults to the value of
|
floor_day |
when |
numeric |
if |
factor |
if |
... |
arguments passed to |
Weeks differ in their start dates depending on context. The ISO 8601 standard specifies that Monday starts the week (https://en.wikipedia.org/wiki/ISO_week_date) while the US CDC uses Sunday as the start of the week (https://wwwn.cdc.gov/nndss/document/MMWR_Week_overview.pdf). For example, MSF has varying start dates depending on country in order to better coordinate response.
While there are packages that provide conversion for ISOweeks and epiweeks, these do not provide seamless conversion from dates to epiweeks with non-standard start dates. This package provides a lightweight utility to be able to convert each day.
date2week() an aweek object which represents dates in
YYYY-Www-d format where YYYY is the year (associated with the week,
not necessarily the day), Www is the week number prepended by a "W" that
ranges from 01-53 and d is the day of the week from 1 to 7 where 1
represents the first day of the week (as defined by the week_start
attribute).
week2date() a Date object.
date2week() will initially convert the input with as.POSIXlt() and
use that to calculate the week. If the user supplies character input, it
is expected that the input will be of the format yyyy-mm-dd unless the
user explicitly passes the "format" parameter to as.POSIXlt(). If the
input is not in yyyy-mm-dd and the format parameter is not passed,
date2week() will result in an error.
Zhian N. Kamvar
set_week_start(), as.Date.aweek(), print.aweek(), as.aweek(),
get_aweek()
## Dates to weeks ----------------------------------------------------------- # The same set of days will occur in different weeks depending on the start # date. Here we can define a week before and after today print(dat <- as.Date("2018-12-31") + -6:7) # By default, the weeks are defined as ISO weeks, which start on Monday print(iso_dat <- date2week(dat)) # This can be changed by setting the global default with set_week_start() set_week_start("Sunday") date2week(dat) # If you want lubridate-style numeric-only weeks, you need look no further # than the "numeric" argument date2week(dat, numeric = TRUE) # To aggregate weeks, you can use `floor_day = TRUE` date2week(dat, floor_day = TRUE) # If you want aggregations into factors that include missing weeks, use # `floor_day = TRUE, factor = TRUE`: date2week(dat[c(1, 14)], floor_day = TRUE, factor = TRUE) ## Weeks to dates ----------------------------------------------------------- # The aweek class can be converted back to a date with `as.Date()` as.Date(iso_dat) # If you don't have an aweek class, you can use week2date(). Note that the # week_start variable is set by the "aweek.week_start" option, which we will # set to Monday: set_week_start("Monday") week2date("2019-W01-1") # 2018-12-31 # This can be overidden by the week_start argument; week2date("2019-W01-1", week_start = "Sunday") # 2018-12-30 # If you want to convert to the first day of the week, you can use the # `floor_day` argument as.Date(iso_dat, floor_day = TRUE) ## The same two week timespan starting on different days -------------------- # ISO week definition: Monday -- 1 date2week(dat, 1) date2week(dat, "Monday") # Tuesday -- 2 date2week(dat, 2) date2week(dat, "Tuesday") # Wednesday -- 3 date2week(dat, 3) date2week(dat, "W") # you can use valid abbreviations # Thursday -- 4 date2week(dat, 4) date2week(dat, "Thursday") # Friday -- 5 date2week(dat, 5) date2week(dat, "Friday") # Saturday -- 6 date2week(dat, 6) date2week(dat, "Saturday") # Epiweek definition: Sunday -- 7 date2week(dat, 7) date2week(dat, "Sunday")## Dates to weeks ----------------------------------------------------------- # The same set of days will occur in different weeks depending on the start # date. Here we can define a week before and after today print(dat <- as.Date("2018-12-31") + -6:7) # By default, the weeks are defined as ISO weeks, which start on Monday print(iso_dat <- date2week(dat)) # This can be changed by setting the global default with set_week_start() set_week_start("Sunday") date2week(dat) # If you want lubridate-style numeric-only weeks, you need look no further # than the "numeric" argument date2week(dat, numeric = TRUE) # To aggregate weeks, you can use `floor_day = TRUE` date2week(dat, floor_day = TRUE) # If you want aggregations into factors that include missing weeks, use # `floor_day = TRUE, factor = TRUE`: date2week(dat[c(1, 14)], floor_day = TRUE, factor = TRUE) ## Weeks to dates ----------------------------------------------------------- # The aweek class can be converted back to a date with `as.Date()` as.Date(iso_dat) # If you don't have an aweek class, you can use week2date(). Note that the # week_start variable is set by the "aweek.week_start" option, which we will # set to Monday: set_week_start("Monday") week2date("2019-W01-1") # 2018-12-31 # This can be overidden by the week_start argument; week2date("2019-W01-1", week_start = "Sunday") # 2018-12-30 # If you want to convert to the first day of the week, you can use the # `floor_day` argument as.Date(iso_dat, floor_day = TRUE) ## The same two week timespan starting on different days -------------------- # ISO week definition: Monday -- 1 date2week(dat, 1) date2week(dat, "Monday") # Tuesday -- 2 date2week(dat, 2) date2week(dat, "Tuesday") # Wednesday -- 3 date2week(dat, 3) date2week(dat, "W") # you can use valid abbreviations # Thursday -- 4 date2week(dat, 4) date2week(dat, "Thursday") # Friday -- 5 date2week(dat, 5) date2week(dat, "Friday") # Saturday -- 6 date2week(dat, 6) date2week(dat, "Saturday") # Epiweek definition: Sunday -- 7 date2week(dat, 7) date2week(dat, "Sunday")
Coerce an aweek object to factor to include missing weeks
factor_aweek(x)factor_aweek(x)
x |
an aweek object |
an aweek object that inherits from factor() with levels that span
the range of the weeks in the object.
when factored aweek objects are combined with other aweek objects, they are converted back to characters.
w <- get_aweek(week = (1:2) * 5, year = 2019, day = c(7, 1)) w wf <- factor_aweek(w) wf # factors are destroyed if combined with aweek objects c(w, wf)w <- get_aweek(week = (1:2) * 5, year = 2019, day = c(7, 1)) w wf <- factor_aweek(w) wf # factors are destroyed if combined with aweek objects c(w, wf)
These are vectorized functions that take integer vectors and return Date or an aweek objects, making it easier to convert bare weeks to dates.
get_aweek( week = 1L, year = format(Sys.Date(), "%Y"), day = 1L, start = week_start, week_start = get_week_start(), ... ) get_date( week = 1L, year = format(Sys.Date(), "%Y"), day = 1L, start = get_week_start() )get_aweek( week = 1L, year = format(Sys.Date(), "%Y"), day = 1L, start = week_start, week_start = get_week_start(), ... ) get_date( week = 1L, year = format(Sys.Date(), "%Y"), day = 1L, start = get_week_start() )
week |
an integer vector, defaults to 1, representing the first week of the year. |
year |
an integer vector, defaults to the current year |
day |
an integer vector, defaults to 1, representing the first day of the first week of the year. |
start |
an integer (or character) vector of days that the weeks
start on for each corresponding week. Defaults to the value of
|
week_start |
a number indicating the start of the week based on the ISO
8601 standard from 1 to 7 where 1 = Monday OR an abbreviation of the
weekdate in an English or current locale. Note: using a non-English locale
may render your code non-portable. Defaults to the value of
|
... |
parameters passed on to |
get_aweek(): an aweek object
get_date(): a Date object
Any missing weeks, years, or start elements will result in a missing element in the resulting vector. Any missing days will revert to the first day of the week.
as.aweek() date2week() week2date()
# The default results in the first week of the year using the default # default week_start (from get_week_start()) get_aweek() get_date() # this is equivalent to as.Date(get_week()), but faster # Some years, like 2015, have 53 weeks get_aweek(53, 2015) # If you specify 53 weeks for a year that doesn't have 53 weeks, aweek will # happily correct it for you get_aweek(53, 2014) # this will be 2015-W01-1 # you can use this to quickly make a week without worrying about formatting # here, you can define an observation interval of 20 weeks obs_start <- get_date(week = 10, year = 2018) obs_end <- get_date(week = 29, year = 2018, day = 7) c(obs_start, obs_end) # If you have a data frame of weeks, you can use it to convert easily mat <- matrix(c( 2019, 11, 1, 7, # 2019-03-10 2019, 11, 2, 7, 2019, 11, 3, 7, 2019, 11, 4, 7, 2019, 11, 5, 7, 2019, 11, 6, 7, 2019, 11, 7, 7 ), ncol = 4, byrow = TRUE) colnames(mat) <- c("year", "week", "day", "start") m <- as.data.frame(mat) m sun <- with(m, get_date(week, year, day, start)) sun as.aweek(sun) # convert to aweek starting on the global week_start as.aweek(sun, week_start = "Sunday") # convert to aweek starting on Sunday # You can also change starts mon <- with(m, get_aweek(week, year, day, "Monday", week_start = "Monday")) mon as.Date(mon) # If you use multiple week starts, it will convert to date and then to # the correct week, so it won't appear to match up with the original # data frame. sft <- with(m, get_aweek(week, year, day, 7:1, week_start = "Sunday")) sft as.Date(sft)# The default results in the first week of the year using the default # default week_start (from get_week_start()) get_aweek() get_date() # this is equivalent to as.Date(get_week()), but faster # Some years, like 2015, have 53 weeks get_aweek(53, 2015) # If you specify 53 weeks for a year that doesn't have 53 weeks, aweek will # happily correct it for you get_aweek(53, 2014) # this will be 2015-W01-1 # you can use this to quickly make a week without worrying about formatting # here, you can define an observation interval of 20 weeks obs_start <- get_date(week = 10, year = 2018) obs_end <- get_date(week = 29, year = 2018, day = 7) c(obs_start, obs_end) # If you have a data frame of weeks, you can use it to convert easily mat <- matrix(c( 2019, 11, 1, 7, # 2019-03-10 2019, 11, 2, 7, 2019, 11, 3, 7, 2019, 11, 4, 7, 2019, 11, 5, 7, 2019, 11, 6, 7, 2019, 11, 7, 7 ), ncol = 4, byrow = TRUE) colnames(mat) <- c("year", "week", "day", "start") m <- as.data.frame(mat) m sun <- with(m, get_date(week, year, day, start)) sun as.aweek(sun) # convert to aweek starting on the global week_start as.aweek(sun, week_start = "Sunday") # convert to aweek starting on Sunday # You can also change starts mon <- with(m, get_aweek(week, year, day, "Monday", week_start = "Monday")) mon as.Date(mon) # If you use multiple week starts, it will convert to date and then to # the correct week, so it won't appear to match up with the original # data frame. sft <- with(m, get_aweek(week, year, day, 7:1, week_start = "Sunday")) sft as.Date(sft)
The aweek class is a character or factor in the format YYYY-Www(-d) with a "week_start" attribute containing an integer specifying which day of the ISO 8601 week each week should begin.
## S3 method for class 'aweek' print(x, ...) ## S3 method for class 'aweek' x[i] ## S3 method for class 'aweek' x[[i]] ## S3 replacement method for class 'aweek' x[i] <- value ## S3 method for class 'aweek' as.list(x, ...) ## S3 method for class 'aweek' trunc(x, ...) ## S3 method for class 'aweek' rep(x, ...) ## S3 method for class 'aweek' c(..., recursive = FALSE, use.names = TRUE)## S3 method for class 'aweek' print(x, ...) ## S3 method for class 'aweek' x[i] ## S3 method for class 'aweek' x[[i]] ## S3 replacement method for class 'aweek' x[i] <- value ## S3 method for class 'aweek' as.list(x, ...) ## S3 method for class 'aweek' trunc(x, ...) ## S3 method for class 'aweek' rep(x, ...) ## S3 method for class 'aweek' c(..., recursive = FALSE, use.names = TRUE)
x |
an object of class |
... |
a series of |
i |
index for subsetting an aweek object. |
value |
a value to add or replace in an aweek object |
recursive, use.names
|
parameters passed on to |
Weeks differ in their start dates depending on context. The ISO 8601 standard specifies that Monday starts the week (https://en.wikipedia.org/wiki/ISO_week_date) while the US CDC uses Sunday as the start of the week (https://wwwn.cdc.gov/nndss/document/MMWR_Week_overview.pdf). For example, MSF has varying start dates depending on country in order to better coordinate response.
While there are packages that provide conversion for ISOweeks and epiweeks, these do not provide seamless conversion from dates to epiweeks with non-standard start dates. This package provides a lightweight utility to be able to convert each day.
Week numbers are calculated in three steps:
Find the day of the week, relative to the week_start (d). The day of the
week (d) relative to the week start (s) is calculated using the ISO week
day (i) via d = 1L + ((i + (7L - s)) %% 7L).
Find the date that represents midweek (m). The date that represents
midweek is found by subtracting the day of the week (d) from 4 and
adding that number of days to the current date: m = date + (4 - d).
Find the week number (w) by counting the number of days since 1 January
to (m), and use integer division by 7: w = 1L + ((m - yyyy-01-01) %/% 7)
For the weeks around 1 January, the year is determined by the week number. If the month is January, but the week number is 52 or 53, then the year for the week (YYYY) is the calendar year (yyyy) minus 1. However, if the month is December, but the week number is 1, then the year for the week (YYYY) is the calendar year (yyyy) plus 1.
The aweek object is a character vector in either the precise ISO week
format (YYYY-Www-d) or imprecise ISO week format (YYYY-Www) with
a week_start attribute indicating which ISO week day the week begins.
The precise ISO week format can be broken down like this:
YYYY is an ISO week-numbering year, which is the year relative to the week, not the day. For example, the date 2016-01-01 would be represented as 2015-W53-5 (ISO week), because while the date is in the year 2016, the week is still part of the final week of 2015.
Www is the week number, prefixed by the character "W". This ranges from 01 to 52 or 53, depending on whether or not the year has 52 or 53 weeks.
d is a digit representing the weekday where 1 represents the first
day of the week and 7 represents the last day of the week. #'
The attribute week_start represents the first day of the week as an ISO
week day. This defaults to 1, which is Monday. If, for example, an aweek
object represented weeks starting on Friday, then the week_start
attribute would be 5, which is Friday of the ISO week.
Imprecise formats (YYYY-Www) are equivalent to the first day of the week. For example, 2015-W53 and 2015-W53-1 will be identical when converted to date.
an object of class aweek
when combining aweek objects together, you must ensure that they have
the same week_start attribute. You can use change_week_start() to adjust
it.
date2week(), get_aweek(), as.Date.aweek(), change_week_start()
d <- as.Date("2018-12-20") + 1:40 w <- date2week(d, week_start = "Sunday") print(w) # subsetting acts as normal w[1:10] # Combining multiple aweek objects will only work if they have the same # week_start day c(w[1], w[3], w[5], as.aweek(as.Date("2018-12-01"), week_start = "Sunday")) # differing week_start days will throw an error mon <- date2week(as.Date("2018-12-01"), week_start = "Monday") mon try(c(w, mon)) # combining Dates will be coerced to aweek objects under the same rules c(w, Sys.Date()) # truncated aweek objects will be un-truncated w2 <- date2week(d[1:5], week_start = "Sunday", floor_day = TRUE) w2 c(w[1:5], w2)d <- as.Date("2018-12-20") + 1:40 w <- date2week(d, week_start = "Sunday") print(w) # subsetting acts as normal w[1:10] # Combining multiple aweek objects will only work if they have the same # week_start day c(w[1], w[3], w[5], as.aweek(as.Date("2018-12-01"), week_start = "Sunday")) # differing week_start days will throw an error mon <- date2week(as.Date("2018-12-01"), week_start = "Monday") mon try(c(w, mon)) # combining Dates will be coerced to aweek objects under the same rules c(w, Sys.Date()) # truncated aweek objects will be un-truncated w2 <- date2week(d[1:5], week_start = "Sunday", floor_day = TRUE) w2 c(w[1:5], w2)
This is a convenience wrapper around options() and getOption(), which
allows users to input both numeric and character week start values
set_week_start(x = 1L) get_week_start(w = NULL)set_week_start(x = 1L) get_week_start(w = NULL)
x |
a character or integer specifying the day of the week for conversion between dates and weeks. |
w |
if |
for set_week_start, the old value of week_start is returned,
invisibly. For get_week_start, the current value of week_start is
returned.
change_week_start() for changing the week_start attribute of an
aweek object, date2week(), week2date()
# get the current definition of the week start get_week_start() # defaults to Monday (1) getOption("aweek.week_start", 1L) # identical to above # set the week start mon <- set_week_start("Sunday") # set week start to Sunday (7) get_week_start() print(set_week_start(mon)) # reset the default get_week_start() # Get the week_start of a specific aweek object. w <- date2week("2019-05-04", week_start = "Sunday") get_week_start(w)# get the current definition of the week start get_week_start() # defaults to Monday (1) getOption("aweek.week_start", 1L) # identical to above # set the week start mon <- set_week_start("Sunday") # set week start to Sunday (7) get_week_start() print(set_week_start(mon)) # reset the default get_week_start() # Get the week_start of a specific aweek object. w <- date2week("2019-05-04", week_start = "Sunday") get_week_start(w)