将data.frame中的列转换为日期 [英] Convert column in data.frame to date
问题描述
我的数据框
a1 <- c("a","a","b","b","c","d","e","e")
b2 <- c("01.01.2015", "02.02.2015", "14.02.2012", "16.08.2008", "17.06.2003", "31.01.2015", "07.01.2022", "09.05.2001")
c3 <- c("1a", "2b", "3c", "4d", "5e", "6f", "7g", "8h")
d3 <- c(1:8)
df2 <- data.frame(a1,b2,c3,d3, stringsAsFactors = F)
我的代码。
library(dplyr)
library(magrittr)
test <- df2 %>%
group_by(a1) %>%
as.Date(b2, format = "%d.%m.%Y")
as.Date.default(。,b2,format =%d。%m。%Y)错误:
不知道如何将'。'转换为日期类。
Error in as.Date.default(., b2, format = "%d.%m.%Y") : do not know how to convert '.' to class "Date"
好吧,我尝试了以下操作:
Well, I tried without the pipe:
df$b2 <- as.Date(df$b2, format = "%d.%m.%Y")
df $ b2中的错误: closure类型的对象不是子集能够
Error in df$b2 : object of type 'closure' is not subsettable
首先:为什么我得到两个不同的错误消息,因为我(据我所知)正在做同样的事情?
First: Why do I get two different error messages since I am (for my understanding) am doing the same?
第二,为什么我不能将列转换为日期?!
Second, why cant I convert my column to date?!
我应该补充一点,我知道使用 mutate
将列更改为 date
格式。但是我不知道为什么我的方法行不通。
I might should add that I am aware of using mutate
to alter the column as date
format. But I wonder why my approach is not working.
推荐答案
在 mutate $ c内进行转换$ c>
df2 %>%
group_by(a1) %>%
mutate(b2=as.Date(b2, format = "%d.%m.%Y"))
# a1 b2 c3 d3
# (chr) (date) (chr) (int)
#1 a 2015-01-01 1a 1
#2 a 2015-02-02 2b 2
#3 b 2012-02-14 3c 3
#4 b 2008-08-16 4d 4
#5 c 2003-06-17 5e 5
#6 d 2015-01-31 6f 6
#7 e 2022-01-07 7g 7
#8 e 2001-05-09 8h 8
如果只需要进行转换,我们就不会
If we need to do only the transformation, we don't need to group by 'a1'.
mutate(df2, b2= as.Date(b2, format= "%d.%m.%Y")
通过使用%<> ;%
运算符来自 magrittr
,我们可以就地进行转换。
By using %<>%
operator from magrittr
, we can transform in place.
df2 %<>%
mutate(b2= as.Date(b2, format= "%d.%m.%Y")
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