Thanks very much for the response. That was a very good article and
gives me a good appreciation for the history and covers the structure of
the two date/time formats well.
What I was specifically looking for is a feel for the situations when
one format should be used over the other. In my work, I have gotten the
impression that I should just use POSIXct for general useability in
functions and graphics until I need to extract specific date components
such as month, day, year, etc. In those instances, just convert to
POSIXlt and extract needed info. Is this mostly accurate? More
generally, is there a resource that summarizes which date/time objects
to use under which conditions? So far, I have mostly been learning by
trial/error/web searching which eventually is effective, but can be
quite slow.
Thanks
Steve
===============================================
Steven R. Corsi Phone: (608) 821-3835
Research Hydrologist email: srco...@usgs.gov
U.S. Geological Survey
Wisconsin Water Science Center
8505 Research Way
Middleton, WI 53562
===============================================
On 3/28/2012 12:16 PM, Duncan Murdoch wrote:
On 28/03/2012 10:06 AM, Steven R Corsi wrote:
Hello R users
I am searching for a descriptive summary of the use of POSIXlt as
compared to POSIXct date/time formats. I have been using them
extensively for different purposes, but still can't quite understand
when to use which one for the most efficient coding and use. I typically
use them in graphics, comparison of times, interpolation of values
between times, computation of time-series parameters, and so on.
My request is simply to learn if there is a resource out there that
explains the strengths of the use of each format in different situations
and if certain situations require one over the other. My web searches
have turned up basic things like the vector form (POSIXlt) vs the
decimal form (POSIXct), but I could not find specific guidance to
understand when it is best to use one over the other.
The first of the "Other Topics" among the "Technical Papers" available
from the main HTML help page in R should address this.
Duncan Murdoch
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