R strptime issue when using %b to format a date

Question

Before marking as duplicate, I've tried a few other solutions, namely these:

R, strptime(), %b, trying to convert character to date format

strptime, as.POSIXct and as.Date return unexpected NA

But neither seem to work for me.

I'm trying to convert a time format Dec-18 to a POSIXct time (would be 2018-12-01 in this case). I'm attempting to use strptime with %b and %y to achieve this as so:

> strptime("Dec-18", format = "%b-%y")
[1] NA

But obviously it is not working. I'm reading a out about "locales" and such, but the above solutions did not work for me. I attempted the following:

> Sys.setlocale("LC_TIME", "C")
[1] "C"
> strptime("Dec-18", format = "%b-%y")
[1] NA

It was also suggested to use this locale, Sys.setlocale("LC_TIME", "en_GB.UTF-8"), but I get an error when trying to use this:

> Sys.setlocale("LC_TIME", "en_GB.UTF-8")
[1] ""
Warning message:
In Sys.setlocale("LC_TIME", "en_GB.UTF-8") :
  OS reports request to set locale to "en_GB.UTF-8" cannot be honored

Kind of at a loss for what to do here. My abbreviated months seem right based off this:

> month.abb
 [1] "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec"

Here's the version of R that I am running:

R version 3.5.3 (2019-03-11) -- "Great Truth"
Copyright (C) 2019 The R Foundation for Statistical Computing
Platform: x86_64-w64-mingw32/x64 (64-bit)

Thanks in advance.

The month and year does not form a date. Adding a "01" in front of it will R detect it as a date. — yarnabrina, May 15 '19 at 15:08

akrun · Answer 1 · 2019-05-15T15:19:26.910

3

The most simplest solution would be

library(zoo)
as.Date(as.yearmon("Dec-18", "%b-%y"))
#[1] "2018-12-01"

The issue in the OP's code is that strptime or as.Date requires a day too. If it is not there, the format is not complete for a Date. One option would be to paste a day in strptime and it works

strptime(paste0("Dec-18", "-01"), format = "%b-%y-%d")
#[1] "2018-12-01 EST"

edited May 15 '19 at 15:19

answered May 15 '19 at 15:02

akrun

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This works, thanks! Curious to see if anyone knows why base R `strptime` isn't working, but this works in the meantime. – giraffehere May 15 '19 at 15:04
@giraffehere dates include day also – akrun May 15 '19 at 15:17

score 3 · Answer 2 · answered May 15 '19 at 15:09

3

With lubridate, you can do:

parse_date_time("Dec-18", "my")

[1] "2018-12-01 UTC"

answered May 15 '19 at 15:09

tmfmnk

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thanks! this is what I was looking for. – mirkhosro Dec 18 '21 at 18:49

score 2 · Accepted Answer · answered May 15 '19 at 15:14

2

The simplest solution will be this:

as.Date(x = paste0("01-", "Dec-18"),
        format = "%d-%b-%y")
#> [1] "2018-12-01"

format(x = as.Date(x = paste0("01-", "Dec-18"),
                   format = "%d-%b-%y"),
       format = "%b-%y")
#> [1] "Dec-18"

^{Created on 2019-05-15 by the reprex package (v0.2.1)}

R doesn't recognise Dec-18 as date. Add a 01- so that it can detect it as date, and then display as you prefer.

answered May 15 '19 at 15:14

yarnabrina

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Dang, should have tried this. Slight quirk to date formatting I guess, but nice work around. – giraffehere May 15 '19 at 15:26

R strptime issue when using %b to format a date

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