R 데이터프레임 Date형 지정

1 개요[ | ]

R 데이터프레임 날짜형 지정
R 데이터프레임 날짜를 Date형으로 변환
R 데이터프레임 날짜를 Date형으로 지정

Date형은 날짜 연산이 수월하다.

2 문제상황[ | ]

R

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MEM

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df <- read.table( header=T, stringsAsFactors=FALSE, text="
day         fruit    ea
2019-06-01  apple    1
2019-06-11  apple    1
2019-06-21  banana   2
2019-07-01  apple    3
2019-07-11  banana   4
")
df

A data.frame: 5 × 3
day	fruit	ea
<chr>	<chr>	<int>
2019-06-01	apple	1
2019-06-11	apple	1
2019-06-21	banana	2
2019-07-01	apple	3
2019-07-11	banana	4

→ day는 chr(character)형

3 방법1: as.Date() ★[ | ]

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df$day1 <- as.Date(df$day)
df

A data.frame: 5 × 4
day	fruit	ea	day1
<chr>	<chr>	<int>	<date>
2019-06-01	apple	1	2019-06-01
2019-06-11	apple	1	2019-06-11
2019-06-21	banana	2	2019-06-21
2019-07-01	apple	3	2019-07-01
2019-07-11	banana	4	2019-07-11

→ day1은 date형

4 방법2: ymd()[ | ]

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library("lubridate")
df$day2 <- ymd(df$day)
df

Attaching package: ‘lubridate’


The following objects are masked from ‘package:base’:

    date, intersect, setdiff, union

A data.frame: 5 × 5
day	fruit	ea	day1	day2
<chr>	<chr>	<int>	<date>	<date>
2019-06-01	apple	1	2019-06-01	2019-06-01
2019-06-11	apple	1	2019-06-11	2019-06-11
2019-06-21	banana	2	2019-06-21	2019-06-21
2019-07-01	apple	3	2019-07-01	2019-07-01
2019-07-11	banana	4	2019-07-11	2019-07-11

→ day2도 date형

5 같이 보기[ | ]