From jeff.a.ryan at gmail.com  Thu Jan 29 21:27:17 2009
From: jeff.a.ryan at gmail.com (Jeff Ryan)
Date: Thu, 29 Jan 2009 14:27:17 -0600
Subject: [Rd] length of POSIXlt object (PR#13482)
In-Reply-To: <20090128221518.E0F0F282EFF0@mail.pubhealth.ku.dk>
References: <20090128221518.E0F0F282EFF0@mail.pubhealth.ku.dk>
Message-ID: <e8e755250901291227y120e3b6euea68f94fcb7f57be@mail.gmail.com>

Read the docs. POSIXlt is a list of 9 elements. Each element length is
what you think it should be returning.  That is not correct.

?POSIXlt

Details:

     There are two basic classes of date/times.  Class '"POSIXct"'
     represents the (signed) number of seconds since the beginning of
     1970 as a numeric vector.  Class '"POSIXlt"' is a named list of
     vectors representing

> unclass(as.POSIXlt(as.POSIXlt('2007-01-01')+1:11))
$sec
 [1]  1  2  3  4  5  6  7  8  9 10 11

$min
 [1] 0 0 0 0 0 0 0 0 0 0 0

$hour
 [1] 0 0 0 0 0 0 0 0 0 0 0

$mday
 [1] 1 1 1 1 1 1 1 1 1 1 1

$mon
 [1] 0 0 0 0 0 0 0 0 0 0 0

$year
 [1] 107 107 107 107 107 107 107 107 107 107 107

$wday
 [1] 1 1 1 1 1 1 1 1 1 1 1

$yday
 [1] 0 0 0 0 0 0 0 0 0 0 0

$isdst
 [1] 0 0 0 0 0 0 0 0 0 0 0

attr(,"tzone")
[1] ""    "CST" "CDT"


Jeff


On Wed, Jan 28, 2009 at 4:15 PM,  <twoutopias at gmail.com> wrote:
> The length() of a POSIXlt object is given as 9 regardless of the actual
> length. For example:
>
>> make.date.time
> function (year=c(2006,2006),month=c(8,8),day=2:5,hour=13,minute=45)
> {# convert year, etc., into POSIXlt object
> #
> d=as.character(make.date(year,month,day))
> t=paste(hour,minute,sep=":")
> as.POSIXlt(paste(d,t))
> }
>> t=make.date.time()
>> t
> [1] "2006-08-02 13:45:00" "2006-08-03 13:45:00" "2006-08-04 13:45:00"
> [4] "2006-08-05 13:45:00"
>> length(t)
> [1] 9
>> t[1]
> [1] "2006-08-02 13:45:00"
>> length(t[1])
> [1] 9
>
>
>
> --
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-- 
Jeffrey Ryan
jeffrey.ryan at insightalgo.com

ia: insight algorithmics
www.insightalgo.com



[Rd] length of POSIXlt object (PR#13482)
Jeff Ryan