How to use ifelse with dates

Question

I have dates in R in format 01/01/2000

I want to create a column with a category that categorizes my subjects as date of birth before the 01/02/2001 ==1 or after 02/02/2001 ==2. Would this be done with an ifelse?

How would you express this?

Thanks

I want to have a column df$date_category with two factors (1== before and 2== after) in which I categorise the dates from the column df$date using a cutoff of 01/02/2001, so dates before first february 2001 get a 1 and those after get a 2. — Lili
– Lili, Commented Sep 8, 2020 at 18:28

Darren Tsai · Accepted Answer · 2020-09-08 19:03:08Z

1

Option 1 : ifelse()

ifelse(as.Date(date, "%d/%m/%Y") < as.Date("2001-02-02"), 1, 2)
# [1] 1 2 2 2

Option 2

2 - (as.Date(date, "%d/%m/%Y") < as.Date("2001-02-02"))
# [1] 1 2 2 2

Option 3 : findInterval()

findInterval(as.Date(date, "%d/%m/%Y"), as.Date("2001-02-02")) + 1
# [1] 1 2 2 2

Data

date <- c("01/02/2001", "02/02/2001", "03/02/2001", "04/02/2001")

answered Sep 8, 2020 at 19:03

Darren Tsai

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Comments

nadjib amrouche · Accepted Answer · 2020-09-08 18:33:41Z

0

it depends of the formats and you have to add the function "as.Date()

for example :

dates <- c("01-02-2001", "30-01-2001", "15-05-2001", "08-10-1992","08-09-2020")

adates=as.Date(dates, "%d-%m-%Y")

ifelse(adates>as.Date("01-02-2001","%d-%m-%Y"),1,0)

answered Sep 8, 2020 at 18:33

nadjib amrouche

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