[R] Truncating dates (and other date-time manipulations)

[Jeff Ryan]

One last item that could be of use:

?timeBasedSeq

Lets you create ranges in any standard format, with simple ISO style
formatting. The level of detail you specify is interpreted as the resolution
that is desired.

e.g.
> timeBasedSeq(2000/2008)
[1] "2000-01-01" "2001-01-01" "2002-01-01" "2003-01-01" "2004-01-01"
[6] "2005-01-01" "2006-01-01" "2007-01-01" "2008-01-01"

> timeBasedSeq(2000/200012)
 [1] "Jan 2000" "Feb 2000" "Mar 2000" "Apr 2000" "May 2000" "Jun 2000"
 [7] "Jul 2000" "Aug 2000" "Sep 2000" "Oct 2000" "Nov 2000" "Dec 2000"

> timeBasedSeq(2000/200012, 'Date')
 [1] "2000-01-01" "2000-02-01" "2000-03-01" "2000-04-01" "2000-05-01"
 [6] "2000-06-01" "2000-07-01" "2000-08-01" "2000-09-01" "2000-10-01"
[11] "2000-11-01" "2000-12-01"

> timeBasedSeq(2000/20000115)
 [1] "2000-01-01" "2000-01-02" "2000-01-03" "2000-01-04" "2000-01-05"
 [6] "2000-01-06" "2000-01-07" "2000-01-08" "2000-01-09" "2000-01-10"
[11] "2000-01-11" "2000-01-12" "2000-01-13" "2000-01-14" "2000-01-15"

> timeBasedSeq(2000/2000010110)
 [1] "2000-01-01 00:00:00 CST" "2000-01-01 01:00:00 CST"
 [3] "2000-01-01 02:00:00 CST" "2000-01-01 03:00:00 CST"
 [5] "2000-01-01 04:00:00 CST" "2000-01-01 05:00:00 CST"
 [7] "2000-01-01 06:00:00 CST" "2000-01-01 07:00:00 CST"
 [9] "2000-01-01 08:00:00 CST" "2000-01-01 09:00:00 CST"
[11] "2000-01-01 10:00:00 CST"
> 


Jeff Ryan wrote:
> 
> I'm still not entirely sure I follow the desired usage, as the original
> post made no reference to ggplot2, but as Gabor mentioned the yearmon etc
> stuff is quite useful.
> 
> If you are formatting arbitrary precision dates, take a look at
> axTicksByTime in xts.  Both xts and quantmod use it for plotting.  The
> core calculation is from ?endpoints
> 
> I think the effect is what you desire --- though the logic of the function
> may be more than you want/need.  I use it within the package(s) to make
> intelligent breaks given the periodicity of the data.
> 
> Some examples are at:   http://www.quantmod.com http://www.quantmod.com 
> 
> My presentation slides from July's Rmetrics conference in Switzerland are
> posted here:  http://www.quantmod.com/Rmetrics2008/
> http://www.quantmod.com/Rmetrics2008/ 
> 
> Most of the functions you have written are somewhere within xts already. 
> At least the functionality is. See the vignette: 
> http://cran.r-project.org/web/packages/xts/index.html
> http://cran.r-project.org/web/packages/xts/index.html 
> 
> Jeff  
> 
> 

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