[R] date

[David Stevens]

Val

Another all-base R solution:

as.Date(strptime(gs$date,format="%m/%d/%y"))

or if you want to add a time field later

as.POSIXct(strptime(gs$date,format="%m/%d/%y")))

since strptime produces a list version of the date: class is POSIXt and the subclass is POSIXlt, that can be convenient for extracting elements like month, day of the year, minute, etc. The actual date/time information is returned as the number of seconds since 1970-01-01 00:00:00 UTC but the representation is as in your gs.d1 below.

It can be a bit tricky when daylight savings time comes into play but that's for another post.

David


On 12/17/2019 3:51 PM, Val wrote:

Hi All,

I wanted to to convert character date  mm/dd/yy  to YYYY-mm-dd
The sample data and my attempt is shown below

gs <-read.table(text="ID date
A1   09/27/03
A2   05/27/16
A3   01/25/13
A4   09/27/19",header=TRUE,stringsAsFactors=F)

Desired output
  ID     date      d1
 A1 09/27/03 2003-09-27
 A2 05/27/16 2016-05-27
 A3 01/25/13 2012-04-25
 A4 09/27/19 2019-09-27

I used this
gs$d1 = as.Date(as.character(gs$date), format = "%Y-%m-%d")

but I got NA's.

How do I get my desired result?
Thank you.

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David K Stevens, PhD, PE
Environmental Engineering Division
Civil and Environmental Engineering
Utah State University
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