[Rd] cut.Date and cut.POSIXt problem

Roger D. Peng rpeng at jhsph.edu
Tue Mar 18 19:58:21 CET 2008


Seems changes in r44116 force the interval to be single months (or years) 
instead of whatever the user specified.  I think the attached patches correct this.

Interestingly, 'cut' and 'seq' allow for the 'breaks' specification to be 
something like "3 months" but the documentation for 'hist' does not allow for 
this type of specification.

-roger

Gabor Grothendieck wrote:
> cut.Date and cut.POSIXt indicate that the breaks argument
> can be an integer followed by a space followed by "year", etc.
> but it seems the integer is ignored.
> 
> For example, I assume that breaks = "3 months" is supposed
> to cut it into quarters but, in fact, it cuts it into months as if
> 3 had not been there.
> 
>> d <- seq(Sys.Date(), length = 12, by = "month")
>> cut(d, "3 months")
>  [1] 2008-03-01 2008-04-01 2008-05-01 2008-06-01 2008-07-01 2008-08-01
> 2008-09-01 2008-10-01 2008-11-01 2008-12-01 2009-01-01 2009-02-01
> Levels: 2008-03-01 2008-04-01 2008-05-01 2008-06-01 2008-07-01
> 2008-08-01 2008-09-01 2008-10-01 2008-11-01 2008-12-01 2009-01-01
> 2009-02-01
>> cut(as.POSIXct(d), "3 months")
>  [1] 2008-03-01 2008-04-01 2008-05-01 2008-06-01 2008-07-01 2008-08-01
> 2008-09-01 2008-10-01 2008-11-01 2008-12-01 2009-01-01 2009-02-01
> Levels: 2008-03-01 2008-04-01 2008-05-01 2008-06-01 2008-07-01
> 2008-08-01 2008-09-01 2008-10-01 2008-11-01 2008-12-01 2009-01-01
> 2009-02-01
>> cut(as.POSIXlt(d), "3 months")
>  [1] 2008-03-01 2008-04-01 2008-05-01 2008-06-01 2008-07-01 2008-08-01
> 2008-09-01 2008-10-01 2008-11-01 2008-12-01 2009-01-01 2009-02-01
> Levels: 2008-03-01 2008-04-01 2008-05-01 2008-06-01 2008-07-01
> 2008-08-01 2008-09-01 2008-10-01 2008-11-01 2008-12-01 2009-01-01
> 2009-02-01
> 
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> 

-- 
Roger D. Peng  |  http://www.biostat.jhsph.edu/~rpeng/
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