Determine if a day of the week exists between two dates in R
[Update]
In another thread, the answer from @Frank solves the problem. This question becomes a duplicate of the other.
[Question]
I am writing a function in R
to check if the day of the week is between two dates. Here is what I have, but I think the solution is not elegant. Is there a more mathematical way to do this?
library(data.table) ## wday is a function in this package
isDayIn <- function(weekday, date1, date2) {
if (weekday<1 | weekday>7) stop("weekday must be an integer from 1 to 7.")
date1 <- as.Date(date1)
date2 <- as.Date(date2)
output <- weekday %in% unique(wday(seq.Date(date1, date2, by=1)))
return(output)
}
## 2015-08-02 is a Sunday and 2015-08-03 is a Monday
isDayIn(1, "2015-08-02", "2015-08-03")
> TRUE
isDayIn(7, "2015-08-02", "2015-08-03")
> FALSE
Note: The function wday
starts on Sunday and ends on Saturday, so Sunday will display in integer 1 and on Saturday it will display integer 7.
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Another function parameter with base R
:
isDayIn <- function(weekday, date1, date2) {
if (weekday<1 | weekday>7) stop("weekday must be an integer from 1 to 7.")
weekday %in% strftime(seq(as.Date(date1), as.Date(date2), by="day"), format="%w")
}
isDayIn(1, "2015-08-02", "2015-08-03")
[1] TRUE
isDayIn(7, "2015-08-02", "2015-08-03")
[1] FALSE
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I think your solution is fine. But here's a quick solution:
isDayIn <- function(weekday, date1, date2) {
if (weekday<1 | weekday>7) stop("weekday must be an integer from 1 to 7.")
require(lubridate)
date1 <- as.Date(date1)
date2 <- as.Date(date2)
if (as.integer(date2 - date1) >= 7) {
return(TRUE) # by default
} else {
return(weekday %in% wday(seq.Date(date1, date2, by=1)))
}
}
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There are already good solutions out there, but none of them allows you to generate a sequence of days. I tried to find a solution that just compares the number of days of the week (and weeks). It uses the internal environment as the first day of the week, but the argument startWithSunday
provides an option to set Sunday as day 1. An alternative would be to switch between %V
and %U
at strftime
, but this approach seems clearer to me.
isDayIn1 <- function(weekday, date1, date2, startWithSunday = FALSE) {
if (weekday < 1 | weekday > 7) stop("weekday must be an integer from 1 to 7.")
if(startWithSunday) {
weekday <- max(weekday - 1, 1)
}
dates <- sort(as.Date(c(date1, date2)))
if (dates[2] - dates[1] >= 7) return(TRUE)
weeks <- strftime(dates, "%V")
days <- strftime(dates, "%u")
if (weeks[1] == weeks[2]) { # Dates are in the same week.
return(weekday >= days[1] & weekday <= days[2])
} else { # Different weeks.
return(weekday >= days[1] | weekday <= days[2])
}
}
The function looks like a lot of code for such a small task, but most of it is just preparation; the actual work is done in two statements return
. The trick is to distinguish between cases where dates are within the same number in different weeks, because this affects the comparison we have to do.
To test if this works isDayIn1
, I wrote this little wrapper:
niceTests <- function(weekday, date1, date2, startWithSunday = FALSE) {
date1 <- as.Date(date1)
date2 <- as.Date(date2)
fmt <- "%a, %y-%m-%d (week %V)"
if (startWithSunday) {
fmt <- "%a, %y-%m-%d (week %U)"
}
print(sprintf("Date1: %s, Date2: %s, Diff.: %d. Range contains day #%d: %s",
strftime(date1, fmt),
strftime(date2, fmt),
abs(date2 - date1),
weekday,
as.character(isDayIn1(weekday, date1, date2, startWithSunday))
))
}
And here is the first group of tests. Note that startWithSunday
the default is - FALSE
, so here weekday 1
means Monday.
niceTests(7, "2015-08-02", "2015-08-03") # from question (Sunday in Su-Mo)
niceTests(6, "2015-08-02", "2015-08-03") # from question (Saturday in Su-Mo)
niceTests(1, "2015-08-02", "2015-08-09") # Full week or more.
niceTests(1, "2015-08-02", "2015-08-10") # Full week or more.
niceTests(1, "2015-08-05", "2015-08-07") # Same week. (Wednesday - Friday)
niceTests(2, "2015-08-05", "2015-08-07") # Same week.
niceTests(3, "2015-08-05", "2015-08-07") # Same week.
niceTests(4, "2015-08-05", "2015-08-07") # Same week.
niceTests(5, "2015-08-05", "2015-08-07") # Same week.
niceTests(6, "2015-08-05", "2015-08-07") # Same week.
niceTests(7, "2015-08-05", "2015-08-07") # Same week.
niceTests(1, "2015-08-08", "2015-08-11") # Across weeks. (Saturday - Tuesday)
niceTests(2, "2015-08-08", "2015-08-11") # Across weeks.
niceTests(3, "2015-08-08", "2015-08-11") # Across weeks.
niceTests(4, "2015-08-08", "2015-08-11") # Across weeks.
niceTests(5, "2015-08-08", "2015-08-11") # Across weeks.
niceTests(6, "2015-08-08", "2015-08-11") # Across weeks.
niceTests(7, "2015-08-08", "2015-08-11") # Across weeks.
Output:
[1] "Date1: Sun, 15-08-02 (week 31), Date2: Mon, 15-08-03 (week 32), Diff.: 1. Range contains day #7: TRUE"
[1] "Date1: Sun, 15-08-02 (week 31), Date2: Mon, 15-08-03 (week 32), Diff.: 1. Range contains day #6: FALSE"
[1] "Date1: Sun, 15-08-02 (week 31), Date2: Sun, 15-08-09 (week 32), Diff.: 7. Range contains day #1: TRUE"
[1] "Date1: Sun, 15-08-02 (week 31), Date2: Mon, 15-08-10 (week 33), Diff.: 8. Range contains day #1: TRUE"
[1] "Date1: Wed, 15-08-05 (week 32), Date2: Fri, 15-08-07 (week 32), Diff.: 2. Range contains day #1: FALSE"
[1] "Date1: Wed, 15-08-05 (week 32), Date2: Fri, 15-08-07 (week 32), Diff.: 2. Range contains day #2: FALSE"
[1] "Date1: Wed, 15-08-05 (week 32), Date2: Fri, 15-08-07 (week 32), Diff.: 2. Range contains day #3: TRUE"
[1] "Date1: Wed, 15-08-05 (week 32), Date2: Fri, 15-08-07 (week 32), Diff.: 2. Range contains day #4: TRUE"
[1] "Date1: Wed, 15-08-05 (week 32), Date2: Fri, 15-08-07 (week 32), Diff.: 2. Range contains day #5: TRUE"
[1] "Date1: Wed, 15-08-05 (week 32), Date2: Fri, 15-08-07 (week 32), Diff.: 2. Range contains day #6: FALSE"
[1] "Date1: Wed, 15-08-05 (week 32), Date2: Fri, 15-08-07 (week 32), Diff.: 2. Range contains day #7: FALSE"
[1] "Date1: Sat, 15-08-08 (week 32), Date2: Tue, 15-08-11 (week 33), Diff.: 3. Range contains day #1: TRUE"
[1] "Date1: Sat, 15-08-08 (week 32), Date2: Tue, 15-08-11 (week 33), Diff.: 3. Range contains day #2: TRUE"
[1] "Date1: Sat, 15-08-08 (week 32), Date2: Tue, 15-08-11 (week 33), Diff.: 3. Range contains day #3: FALSE"
[1] "Date1: Sat, 15-08-08 (week 32), Date2: Tue, 15-08-11 (week 33), Diff.: 3. Range contains day #4: FALSE"
[1] "Date1: Sat, 15-08-08 (week 32), Date2: Tue, 15-08-11 (week 33), Diff.: 3. Range contains day #5: FALSE"
[1] "Date1: Sat, 15-08-08 (week 32), Date2: Tue, 15-08-11 (week 33), Diff.: 3. Range contains day #6: TRUE"
[1] "Date1: Sat, 15-08-08 (week 32), Date2: Tue, 15-08-11 (week 33), Diff.: 3. Range contains day #7: TRUE"
Finally, tests for startWidthSunday = TRUE
where day 1 is Sunday:
print("Now: Start with Sunday!")
niceTests(1, "2015-08-02", "2015-08-03", startWithSunday = TRUE) # from question (Sunday in Su-Mo)
niceTests(7, "2015-08-02", "2015-08-03", startWithSunday = TRUE) # from question (Saturday in Su-Mo)
niceTests(1, "2015-08-02", "2015-08-09", startWithSunday = TRUE) # Full week or more.
niceTests(1, "2015-08-02", "2015-08-10", startWithSunday = TRUE) # Full week or more.
niceTests(1, "2015-08-05", "2015-08-07", startWithSunday = TRUE) # Same week. (Wednesday - Friday)
niceTests(2, "2015-08-05", "2015-08-07", startWithSunday = TRUE) # Same week.
niceTests(3, "2015-08-05", "2015-08-07", startWithSunday = TRUE) # Same week.
niceTests(4, "2015-08-05", "2015-08-07", startWithSunday = TRUE) # Same week.
niceTests(5, "2015-08-05", "2015-08-07", startWithSunday = TRUE) # Same week.
niceTests(6, "2015-08-05", "2015-08-07", startWithSunday = TRUE) # Same week.
niceTests(7, "2015-08-05", "2015-08-07", startWithSunday = TRUE) # Same week.
niceTests(1, "2015-08-08", "2015-08-11", startWithSunday = TRUE) # Across weeks. (Saturday - Tuesday)
niceTests(2, "2015-08-08", "2015-08-11", startWithSunday = TRUE) # Across weeks.
niceTests(3, "2015-08-08", "2015-08-11", startWithSunday = TRUE) # Across weeks.
niceTests(4, "2015-08-08", "2015-08-11", startWithSunday = TRUE) # Across weeks.
niceTests(5, "2015-08-08", "2015-08-11", startWithSunday = TRUE) # Across weeks.
niceTests(6, "2015-08-08", "2015-08-11", startWithSunday = TRUE) # Across weeks.
niceTests(7, "2015-08-08", "2015-08-11", startWithSunday = TRUE) # Across weeks.
Output:
[1] "Now: Start with Sunday!"
[1] "Date1: Sun, 15-08-02 (week 31), Date2: Mon, 15-08-03 (week 31), Diff.: 1. Range contains day #1: TRUE"
[1] "Date1: Sun, 15-08-02 (week 31), Date2: Mon, 15-08-03 (week 31), Diff.: 1. Range contains day #7: FALSE"
[1] "Date1: Sun, 15-08-02 (week 31), Date2: Sun, 15-08-09 (week 32), Diff.: 7. Range contains day #1: TRUE"
[1] "Date1: Sun, 15-08-02 (week 31), Date2: Mon, 15-08-10 (week 32), Diff.: 8. Range contains day #1: TRUE"
[1] "Date1: Wed, 15-08-05 (week 31), Date2: Fri, 15-08-07 (week 31), Diff.: 2. Range contains day #1: FALSE"
[1] "Date1: Wed, 15-08-05 (week 31), Date2: Fri, 15-08-07 (week 31), Diff.: 2. Range contains day #2: FALSE"
[1] "Date1: Wed, 15-08-05 (week 31), Date2: Fri, 15-08-07 (week 31), Diff.: 2. Range contains day #3: FALSE"
[1] "Date1: Wed, 15-08-05 (week 31), Date2: Fri, 15-08-07 (week 31), Diff.: 2. Range contains day #4: TRUE"
[1] "Date1: Wed, 15-08-05 (week 31), Date2: Fri, 15-08-07 (week 31), Diff.: 2. Range contains day #5: TRUE"
[1] "Date1: Wed, 15-08-05 (week 31), Date2: Fri, 15-08-07 (week 31), Diff.: 2. Range contains day #6: TRUE"
[1] "Date1: Wed, 15-08-05 (week 31), Date2: Fri, 15-08-07 (week 31), Diff.: 2. Range contains day #7: FALSE"
[1] "Date1: Sat, 15-08-08 (week 31), Date2: Tue, 15-08-11 (week 32), Diff.: 3. Range contains day #1: TRUE"
[1] "Date1: Sat, 15-08-08 (week 31), Date2: Tue, 15-08-11 (week 32), Diff.: 3. Range contains day #2: TRUE"
[1] "Date1: Sat, 15-08-08 (week 31), Date2: Tue, 15-08-11 (week 32), Diff.: 3. Range contains day #3: TRUE"
[1] "Date1: Sat, 15-08-08 (week 31), Date2: Tue, 15-08-11 (week 32), Diff.: 3. Range contains day #4: FALSE"
[1] "Date1: Sat, 15-08-08 (week 31), Date2: Tue, 15-08-11 (week 32), Diff.: 3. Range contains day #5: FALSE"
[1] "Date1: Sat, 15-08-08 (week 31), Date2: Tue, 15-08-11 (week 32), Diff.: 3. Range contains day #6: FALSE"
[1] "Date1: Sat, 15-08-08 (week 31), Date2: Tue, 15-08-11 (week 32), Diff.: 3. Range contains day #7: TRUE"
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