R help - May 2008 - Strptime

Hi

This code should explain what I'm trying to do
> strptime("30-Jan-08", "%d-%b-%y")
[1] "2008-01-30"
> 
> format(strptime("30-Jan-08", "%d-%b-%y") ,
"%b-%y")
[1] "Jan-08"
> 
> strptime(format(strptime("30-Jan-08", "%d-%b-%y") ,
"%b-%y") ,
"%b-%y") 
[1] NA


I have a string of the form "Jan-08" but I can't seem to get
strptime to
recognise it. The format function can take the date object and using the
given flags "%b-%y" create a string. It can't, however, seem to go
back
the other way, i.e. as in the line below:
> strptime(format(strptime("30-Jan-08", "%d-%b-%y") ,
"%d-%m-%Y"),
"%d-%m-%Y")
[1] "2008-01-30"

Any tips?

Thanks
Sean





> R.Version()
$platform
[1] "i386-pc-mingw32"

$arch
[1] "i386"

$os
[1] "mingw32"

$system
[1] "i386, mingw32"

$status
[1] ""

$major
[1] "2"

$minor
[1] "6.0"

$year
[1] "2007"

$month
[1] "10"

$day
[1] "03"

$`svn rev`
[1] "43063"

$language
[1] "R"

$version.string
[1] "R version 2.6.0 (2007-10-03)"

On Fri, May 30, 2008 at 12:58:27PM +0100, Creighton, Sean 
wrote:
> Hi
> 
> This code should explain what I'm trying to do
> 
> > strptime("30-Jan-08", "%d-%b-%y")
> [1] "2008-01-30"
> > 
> > format(strptime("30-Jan-08", "%d-%b-%y") ,
"%b-%y")
> [1] "Jan-08"
> > 
> > strptime(format(strptime("30-Jan-08", "%d-%b-%y")
, "%b-%y") ,
> "%b-%y") 
> [1] NA
> 
> 
> I have a string of the form "Jan-08" but I can't seem to get
strptime to
> recognise it. The format function can take the date object and using the
> given flags "%b-%y" create a string. It can't, however, seem
to go back
> the other way, i.e. as in the line below:
> 
> > strptime(format(strptime("30-Jan-08", "%d-%b-%y")
, "%d-%m-%Y"),
> "%d-%m-%Y")
> [1] "2008-01-30"
> 
> Any tips?
Supply (a|any) date to make it a complete date to parse:
> strptime(paste("30", format(strptime("30-Jan-08",
"%d-%b-%y") , "%b-%y"), sep="-"),
"%d-%b-%y")
[1] "2008-01-30"

Dirk

-- 
Three out of two people have difficulties with fractions.

As yearmon in the zoo package can convert a month/year to
an object of class "yearmon" and that can be converted to other
classes, e.g.
> library(zoo)
> x <- "Jan-08"
> as.Date(as.yearmon(x, "%b-%y"))
[1] "2008-01-01"

On Fri, May 30, 2008 at 7:58 AM, Creighton, Sean
<sean.creighton at citi.com> wrote:
> Hi
>
> This code should explain what I'm trying to do
>
>> strptime("30-Jan-08", "%d-%b-%y")
> [1] "2008-01-30"
>>
>> format(strptime("30-Jan-08", "%d-%b-%y") ,
"%b-%y")
> [1] "Jan-08"
>>
>> strptime(format(strptime("30-Jan-08", "%d-%b-%y") ,
"%b-%y") ,
> "%b-%y")
> [1] NA
>
>
> I have a string of the form "Jan-08" but I can't seem to get
strptime to
> recognise it. The format function can take the date object and using the
> given flags "%b-%y" create a string. It can't, however, seem
to go back
> the other way, i.e. as in the line below:
>
>> strptime(format(strptime("30-Jan-08", "%d-%b-%y") ,
"%d-%m-%Y"),
> "%d-%m-%Y")
> [1] "2008-01-30"
>
> Any tips?
>
> Thanks
> Sean
>
>
>
>
>
>
>> R.Version()
> $platform
> [1] "i386-pc-mingw32"
>
> $arch
> [1] "i386"
>
> $os
> [1] "mingw32"
>
> $system
> [1] "i386, mingw32"
>
> $status
> [1] ""
>
> $major
> [1] "2"
>
> $minor
> [1] "6.0"
>
> $year
> [1] "2007"
>
> $month
> [1] "10"
>
> $day
> [1] "03"
>
> $`svn rev`
> [1] "43063"
>
> $language
> [1] "R"
>
> $version.string
> [1] "R version 2.6.0 (2007-10-03)"
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Hi,

what's wrong with that?
> strptime("06:00:00 03.01.2008",format="%H:%M%:%S
%d.%m.%Y",tz="GMT")
[1] NA

the command seems to comply with the rules in the help file but returns NA
(R 2.6.1 Windows XT)

Eric Elguero