R weekdays 提取 POSIXt 或日期對象的部分內容

說明

提取工作日、月份或季度或儒略時間(自某個來源以來的天數)。這些是通用函數：內部日期時間類的方法記錄在此處。

用法

weekdays(x, abbreviate)
## S3 method for class 'POSIXt'
weekdays(x, abbreviate = FALSE)
## S3 method for class 'Date'
weekdays(x, abbreviate = FALSE)

months(x, abbreviate)
## S3 method for class 'POSIXt'
months(x, abbreviate = FALSE)
## S3 method for class 'Date'
months(x, abbreviate = FALSE)

quarters(x, abbreviate)
## S3 method for class 'POSIXt'
quarters(x, ...)
## S3 method for class 'Date'
quarters(x, ...)

julian(x, ...)
## S3 method for class 'POSIXt'
julian(x, origin = as.POSIXct("1970-01-01", tz = "GMT"), ...)
## S3 method for class 'Date'
julian(x, origin = as.Date("1970-01-01"), ...)

參數

x	從類 "POSIXt" 或 "Date" 繼承的對象。
abbreviate	邏輯向量(可能被回收)。名字應該縮寫嗎？
origin	從類 "POSIXt" 或 "Date" 繼承的長度為 1 的對象。
...	其他方法的參數。

值

weekdays 和 months 返回正在使用的語言環境中的名稱字符向量，即 Sys.getlocale("LC_TIME") 。

quarters 將 "Q1" 的字符向量返回到 "Q4" 。

julian返回自原點以來的天數(可能是小數)，原點為"origin"屬性。所有時間計算在R已忽略leap-seconds。

注意

其他組件(例如月份或年份)非常容易計算：隻需使用 as.POSIXlt 並提取相關組件即可。或者(特別是如果需要將組件作為字符串)，請使用 strftime 。

例子

## first two are locale dependent:
weekdays(.leap.seconds)
months  (.leap.seconds)
quarters(.leap.seconds)

## Show how easily you get month, day, year, day (of {month, week, yr}), ... :
## (remember to count from 0 (!): mon = 0..11, wday = 0..6,  etc !!)

##' Transform (Time-)Date vector  to  convenient data frame :
dt2df <- function(dt, dName = deparse(substitute(dt))) {
    DF <- as.data.frame(unclass(as.POSIXlt( dt )))
    `names<-`(cbind(dt, DF, deparse.level=0L), c(dName, names(DF)))
}
## e.g.,
dt2df(.leap.seconds)    # date+time
dt2df(Sys.Date() + 0:9) # date

##' Even simpler:  Date -> Matrix - dropping time info {sec,min,hour, isdst}
d2mat <- function(x) simplify2array(unclass(as.POSIXlt(x))[4:7])
## e.g.,
d2mat(seq(as.Date("2000-02-02"), by=1, length.out=30)) # has R 1.0.0's release date


## Julian Day Number (JDN, https://en.wikipedia.org/wiki/Julian_day)
## is the number of days since noon UTC on the first day of 4317 BCE.
## in the proleptic Julian calendar.  To more recently, in
## 'Terrestrial Time' which differs from UTC by a few seconds
## See https://en.wikipedia.org/wiki/Terrestrial_Time
julian(Sys.Date(), -2440588) # from a day
floor(as.numeric(julian(Sys.time())) + 2440587.5) # from a date-time

也可以看看

DateTimeClasses，Date； Sys.getlocale("LC_TIME") 對於 months() 和 weekdays() 至關重要。