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https://issues.apache.org/jira/browse/ARROW-16596?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17538219#comment-17538219
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Dragoș Moldovan-Grünfeld edited comment on ARROW-16596 at 5/17/22 1:55 PM:
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I think we would need to if we wanted to emulate the behaviour. I think it
refers to the fact that other parsing functions in lubridate use the parsing
functionality native to R (e.g. R's {{strptime}} as opposed to lubridate's
{{{}fast_strptime){}}}.
I implemented this using the Arrow strptime kernel, but it would definitely be
nice to have this option.
Having said that, it is not crucial, as the users can manipulate strings to add
the first 2 digits and then parse with a {{"%Y-%m-%d"}} format.
was (Author: dragosmg):
I think we would need to if we wanted to emulate the behaviour. I think it
refers to the fact that other parsing functions in lubridate use the parsing
functionality native to R (e.g. R's {{strptime}} as opposed to lubridate's
{{{}fast_strptime){}}}.
I implemented this using the Arrow strptime kernel, but it would definitely be
nice to have this option.
> [C++] Add a strptime option to control the cutoff between 1900 and 2000 when
> %y
> --------------------------------------------------------------------------------
>
> Key: ARROW-16596
> URL: https://issues.apache.org/jira/browse/ARROW-16596
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++, R
> Affects Versions: 8.0.0
> Reporter: Dragoș Moldovan-Grünfeld
> Priority: Major
>
> When parsing to datetime a string with year in the short format ({{{}%y{}}}),
> it would be great if we could have control over the cutoff point between 1900
> and 2000. Currently it is implicitly set to 68:
> {code:r}
> library(arrow, warn.conflicts = FALSE)
> a <- Array$create(c("68-05-17", "69-05-17"))
> call_function("strptime", a, options = list(format = "%y-%m-%d", unit = 0L))
> #> Array
> #> <timestamp[s]>
> #> [
> #> 2068-05-17 00:00:00,
> #> 1969-05-17 00:00:00
> #> ]
> {code}
> For example, lubridate named this argument {{cutoff_2000}} argument (e.g. for
> {{{}fast_strptime){}}}. This works as follows:
> {code:r}
> library(lubridate, warn.conflicts = FALSE)
> dates_vector <- c("68-05-17", "69-05-17", "55-05-17")
> fast_strptime(dates_vector, format = "%y-%m-%d")
> #> [1] "2068-05-17 UTC" "1969-05-17 UTC" "2055-05-17 UTC"
> fast_strptime(dates_vector, format = "%y-%m-%d", cutoff_2000 = 50)
> #> [1] "1968-05-17 UTC" "1969-05-17 UTC" "1955-05-17 UTC"
> fast_strptime(dates_vector, format = "%y-%m-%d", cutoff_2000 = 70)
> #> [1] "2068-05-17 UTC" "2069-05-17 UTC" "2055-05-17 UTC"
> {code}
> In the {{lubridate::fast_strptime()}} documentation it is described as
> follows:
> {quote}cutoff_2000
> integer. For y format, two-digit numbers smaller or equal to cutoff_2000 are
> parsed as though starting with 20, otherwise parsed as though starting with
> 19. Available only for functions relying on lubridates internal parser.
> {quote}
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