仅从r中的日期中提取四分之一 [英] Extract only quarter from a date in r

问题描述

我只想从日期中提取四分之一，例如，从日期 2003-02-08中获取整数1。我一直在尝试沿着这条线

I would like to extract ONLY the quarter from a date, e.g., to get an integer 1 from the date "2003-02-08". I have been trying something along this line

library(mondate)
as.yearqtr(dat$DATE)

2003 Q1

"2003 Q1"

as.character(as.yearqtr(dat$DATE))[1]

2003 Q1

"2003 Q1"

一直没有给我想要的结果。当然，我可以这样写条件

which hasn't been giving my desired result. Of course I can write conditions as follows

library(data.table)
data$DATE = as.Date(data$DATE, format='%d%b%Y')
data$month=month(data$DATE)
setDT(data)[month==1,  quarter:=1]  
    ...

这会起作用，但一点都不优雅。

This will work, but is not elegant at all. Is there a more beautiful way of doing this?

谢谢lmo和user2100721！我真的希望我能接受所有答案！

Thank you lmo and user2100721! I really wish I could accept all of the answers!

推荐答案

我会这样做：

# example data
DT = data.table(id = 1:10, d = as.IDate("2003-02-08") + seq(100, by=50, length.out=10))

DT[, qtr := quarter(d)]

    id          d qtr
 1:  1 2003-05-19   2
 2:  2 2003-07-08   3
 3:  3 2003-08-27   3
 4:  4 2003-10-16   4
 5:  5 2003-12-05   4
 6:  6 2004-01-24   1
 7:  7 2004-03-14   1
 8:  8 2004-05-03   2
 9:  9 2004-06-22   2
10: 10 2004-08-11   3

季度函数由data.table提供，可在 Date 和 IDate 向量上使用。 （ IDate 使用整数存储。）

The quarter function is provided by data.table and works on both Date and IDate vectors. (IDate uses integer storage.)

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