Re: timeDate

[David L Lorenz <lorenz@usgs.gov>]

Laura,
  TimeDate objects store the date
and the integer number of days since 1/1/1960 and time as the integer number
of milliseconds since midnight. So there really are two parts to your question.

  The first (truncating the data)
is important if you wanted to merge observations based on the day or table
the occurrences on each day. To really truncate the data, you can use the
trunc() function.
  The second is for presentation.
To change how dates are displayed, you need to change the format slot.
For example, if you had a vector of timeDate data called Junk, then to
see only the month/day/year:

Junk@format <- "%m/%d/%Y"

  There are several functions that
extract information from timeDate data. The months() function will create
a factor vector of the months.
Dave

Laura Chihara <lchihara@carleton.edu>
Sent by: s-news-owner@lists.biostat.wustl.edu

10/26/2006 01:18 PM

To	s-news@lists.biostat.wustl.edu
cc
Subject	[S] timeDate

How do you truncate the time portion from
a timeDate object.For example, for observations of
times such as 3/20/2006 10:21:50.000
I just want the date 3/20/2006
I want to use table to count the number of occurrences
of 3/20/2006, 3/21/2006, etc.

More generally, how do you extract other parts of the
date - say I want a variable that just keeps
the months (I want to see how many times
March occurs, April occurs, etc.)

Thanks!

-- Laura Chihara

*******************************************
Laura Chihara
Associate Professor    507-646-4065 (office)
Dept of Mathematics    507-646-4312 (fax)
Carleton College
1 North College Street
Northfield MN 55057
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