[R-sig-Geo] POSIX* objects and writeOGR()

[Agustin Lobo]

Thanks!

I see that creating a temporary SPDF with that variable casted
as character is the only way to run writeOGR().

Would it be possible adding
an option i.e. POSIXtoCHAR=T to writeOGR() so that such a conversion is
automated?

Agus

Michael Sumner wrote:
> POSIXlt stores the date-times as a list of vectors decomposed into the
> (still numeric) component parts ("sec", "min", "hour", "mday", "mon",
> "year", "wday", "yday", "isdst") so that cannot be stored as a single
> column in the data frame - you would need 9 columns.
> 
> 
> Compare these to see the underlying structure:
> 
> tm <- Sys.time()
> ## POSIXct
> unclass(tm)
> ## POSIXlt
> unclass(as.POSIXlt(tm))
> 
> You can just cast to character, directly or with format - see
> ?strptime for the full set of format tokens available. For example:
> 
>  as.character(tm)
> ##[1] "2009-12-31 07:28:01"
> format(tm, "%Y/%b/%a %H:%M:%S")
> ##[1] "2009/Dec/Thu 07:28:01"
> 
> Hope that helps.
> 
> Regards, Mike.
> 
> 
> On Thu, Dec 31, 2009 at 7:15 AM, Agustin Lobo <alobolistas at gmail.com> wrote:
>> This might be a bit off-topic.
>> I have to export as shape an Sp.Poly.DF in which
>> one of the variables records date and time as POSIXtc. As
>> writeOGR() complains about the POSIXct variable, I'm
>> trying to convert to POSIXlt, which I think that will be
>> accepted (another alternative would be coverting to an
>> string char, but prefer to keep the SPDF object with
>> a correct class definition for that variable).
>> Let's call patata the table of the SPDF.
>>
>>> class(patata$Tima)
>> [1] "POSIXt"  "POSIXct"
>>
>>> patata$Tima[1]
>> [1] "2009-09-26 09:57:24 CEST"
>>
>>> as.POSIXlt(patata$Tima[1])
>> [1] "2009-09-26 09:57:24 CEST"
>>
>>> class(as.POSIXlt(patata$Tima[1]))
>> [1] "POSIXt"  "POSIXlt"
>>
>> So I was happy, but:
>>
>>> patata$Tima <- as.POSIXlt(patata$Tima)
>> Error in `$<-.data.frame`(`*tmp*`, "Tima", value = list(sec = c(24, 33,  :
>>  replacement has 9 rows, data has 44
>> Calls: $<- -> $<-.data.frame
>>
>>
>> Is there any way I can put the POSIXlt object in the table (patata) of the
>> SPDF object?
>>
>> Thanks!
>>
>> Agus
>>
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>