将R中的日期四舍五入为任意分钟/小时的精度 [英] round a date in R to an arbitrary minute/hour level of precision

问题描述

我希望以任意精度将R中的日期分组.

I'm looking to group dates in R by an arbitrary level of precision.

使用例如 lubridate :

library(lubridate)
nearest_hour = floor_date(now(), 'hour')

然后，您可以将此类日期的列表分组，例如来自 plyr 的简单 summary ddply .

You can then group a list of such dates with e.g. a simple summarise ddply from plyr.

我想做的是以任意精度对日期进行舍入，例如到最近的15分钟或每3个小时一次:

What I'd like to do is round dates with arbitrary precision, e.g. to the nearest 15 minutes or every 3 hours:

nearest_three_hours = floor_date(now(), '3 hours')

在

There's a discussion of such things at http://r.789695.n4.nabble.com/Truncating-dates-and-other-date-time-manipulations-td866901.html but outside of cutting dates, there doesn't appear to have been any resolution.

推荐答案

将已经地板的润滑到最近的原子单元.为了使发言权最接近15分钟(我认为这是您想要做的(而不是四舍五入))，您只需要通过findInterval和一组定义的断点映射到正确的范围即可.试试这个floor_time，它在功能上等同于floor_date，但是允许您为秒，分钟或小时指定可变的单位数.

lubridate already floors to the nearest atomic unit. To get floor to the nearest 15 minutes, which I think is what you want to do (not round), you just need to map into the correct range via findInterval and a defined set of breakpoints. Try this floor_time, which is functionally equivalent to floor_date, but allows you to specify a variable # of units for seconds, minutes or hours.

floor_time <- function(x, k = 1, unit = c("second", "minute", "hour", "day", 
                                          "week", "month", "year")) {
  require(lubridate)

  nmax <- NULL

  switch(unit, second = {nmax <- 60},
         minute = {nmax <- 60},
         hour = {nmax <- 24})

  cuts <- seq(from = 0, to = nmax - 1, by = k)
  new <- switch(unit, 
                second = update(x, seconds = cuts[findInterval(second(x), cuts)]), 
                minute = update(x, minutes = cuts[findInterval(minute(x), cuts)], 
                                seconds = 0), 
                hour = update(x, hours = cuts[findInterval(hour(x), cuts)], 
                              minutes = 0, seconds = 0), 
                day = update(x, hours = 0, minutes = 0, seconds = 0), 
                week = update(x, wdays = 1, hours = 0, minutes = 0, seconds = 0), 
                month = update(x, mdays = 1, hours = 0, minutes = 0, seconds = 0), 
                year = update(x, ydays = 1, hours = 0, minutes = 0, seconds = 0))

  new
}

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