假设我在R中有一个日期，它的格式如下。
date
2012-02-01
2012-02-01
2012-02-02
在R中是否有办法添加另一列，将星期几与日期相关联?数据集非常大，所以手动进行更改是没有意义的。
df = data.frame(date=c("2012-02-01", "2012-02-01", "2012-02-02"))
所以在加上天数之后，它最终会是这样的:
date day
2012-02-01 Wednesday
2012-02-01 Wednesday
2012-02-02 Thursday
这可能吗?谁能给我指出一个允许我这样做的包? 试着按日期自动生成日期。
使用润滑包和功能:
library(lubridate)
df$date <- as.Date(df$date)
wday(df$date, label=TRUE)
[1] Wed Wed Thurs
Levels: Sun < Mon < Tues < Wed < Thurs < Fri < Sat
这应该能奏效
df = data.frame(date=c("2012-02-01", "2012-02-01", "2012-02-02"))
dow <- function(x) format(as.Date(x), "%A")
df$day <- dow(df$date)
df
#Returns:
date day
1 2012-02-01 Wednesday
2 2012-02-01 Wednesday
3 2012-02-02 Thursday
df = data.frame(date=c("2012-02-01", "2012-02-01", "2012-02-02"))
df$day <- weekdays(as.Date(df$date))
df
## date day
## 1 2012-02-01 Wednesday
## 2 2012-02-01 Wednesday
## 3 2012-02-02 Thursday
编辑:只是为了展示另一种方式……
POSIXlt对象的wday组件是数字工作日(从星期天开始是0-6)。
as.POSIXlt(df$date)$wday
## [1] 3 3 4
您可以使用子集工作日名称的字符向量
c("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday",
"Friday", "Saturday")[as.POSIXlt(df$date)$wday + 1]
## [1] "Wednesday" "Wednesday" "Thursday"
假设你想让这一周从周一开始(而不是默认的周日)，那么下面的方法是有用的:
require(lubridate)
df$day = ifelse(wday(df$time)==1,6,wday(df$time)-2)
结果是间隔[0，..，6]中的天数。
如果你想让区间为[1，..7]，使用以下方法:
df$day = ifelse(wday(df$time)==1,7,wday(df$time)-1)
．.． 或者,或者:
df$day = df$day + 1
form注释的JStrahl格式(as.Date(df$date)，"%w")，我们得到当前日期的数字: as.numeric(格式(as.Date(“2016-05-09”)、“% w”))
start = as.POSIXct("2017-09-01")
end = as.POSIXct("2017-09-06")
dat = data.frame(Date = seq.POSIXt(from = start,
to = end,
by = "DSTday"))
# see ?strptime for details of formats you can extract
# day of the week as numeric (Monday is 1)
dat$weekday1 = as.numeric(format(dat$Date, format = "%u"))
# abbreviated weekday name
dat$weekday2 = format(dat$Date, format = "%a")
# full weekday name
dat$weekday3 = format(dat$Date, format = "%A")
dat
# returns
Date weekday1 weekday2 weekday3
1 2017-09-01 5 Fri Friday
2 2017-09-02 6 Sat Saturday
3 2017-09-03 7 Sun Sunday
4 2017-09-04 1 Mon Monday
5 2017-09-05 2 Tue Tuesday
6 2017-09-06 3 Wed Wednesday
