私はlubridate
でこの機能を見つけることができなかったので、私は、少なくとも日付のベクトルの各要素と与えられたエポック間のうるう日の数を計算する機能を書いた:これにより
# count_leap_days: returns an integer for the number of leap days between a
# supplied vector of dates and a fixed epoch
count_leap_days <- function(dates, epoch = ymd('1850-01-01'), proleptic = FALSE)
{
require(lubridate)
# check input
if (!is(epoch, 'Date') | !is(dates, 'Date'))
{
stop('count_leap_days: both arguments must be Date objects.')
}
if (any(dates <= epoch))
{
stop('count_leap_days: dates should all be later than epoch.')
}
if (proleptic = FALSE & epoch < ymd('1582-10-15'))
{
message('count_leap_days: ',
'no leap days before 1582-10-15 unless proleptic = TRUE.')
epoch = ymd('1582-10-15')
}
# get the year range
# exclude start (end) years if they begin after (start before) feb 29
y.epoch = year(epoch) +
ifelse(epoch >= ymd(paste0(year(epoch), '-03-01')), 1, 0)
y.dates = year(dates) -
ifelse(dates <= ymd(paste0(year(dates), '-02-28')), 1, 0)
span = y.dates - y.epoch + 1
# a year is a leap year if it's:
# - divisble by 4. but
# - NOT if it's also divisible by 100, unless
# - it's also divisible by 400.
# all years div. by 4 are also div. by 100, and
# all years div. by 100 are also div. by 400.
# hence, total days = (div. by 4) - (div. by 100) + (div. by 400)
div4 = span %/% 4 +
ifelse(
(y.epoch %% 4) %in% c(0, (4 - (span %% 4) - 1):(4 - 1)) &
(y.dates %% 4) %in% 0:(span %% 4 - 1),
1, 0)
div100 = span %/% 100 +
ifelse(
(y.epoch %% 100) %in% c(0, (100 - (span %% 100) - 1):(100 - 1)) &
(y.dates %% 100) %in% 0:(span %% 100 - 1),
1, 0)
div400 = span %/% 400 +
ifelse(
(y.epoch %% 400) %in% c(0, (400 - (span %% 400) - 1):(400 - 1)) &
(y.dates %% 400) %in% 0:(span %% 400 - 1),
1, 0)
return(div4 - div100 + div400)
}
私は365日のカレンダーからグレゴリオ暦に変換することができます。逃した閏日の数を追加するだけです:
input$date.utc = input$date.utc +
count_leap_days(input$date.utc, epoch = epoch)