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Ben Bolker

2009-Oct-15 17:10 UTC

[Rd] forwarded: bug (?) in cut.POSIXt with "breaks"=integer

From: Vitalie S. <vitosmail <at> rambler.ru>
Subject: Bug in cut.POSIXt
Newsgroups: gmane.comp.lang.r.general
Date: 2009-10-15 15:47:48 GMT (1 hour and 29 minutes ago)

Hello Everyone,

Before reporting decided to post here first:

tt <- structure(c(1254238817, 1254238859, 1254238969, 1254239080), class
c("POSIXt",
                                                             
"POSIXct"),
tzone = "")

cut.POSIXt(tt, 2)
#Error in `levels<-.factor`(`*tmp*`, value = character(0)) :
#  number of levels differs

cut.POSIXt(tt, 2, labels=c("a1", "a2"))
#[1] a1 a1 a2 a2
#Levels: a1 a2

cut(tt, "2 mins")
#[1] 2009-09-29 17:40:00 2009-09-29 17:40:00 2009-09-29 17:42:00
2009-09-29 17:44:00
#Levels: 2009-09-29 17:40:00 2009-09-29 17:42:00 2009-09-29 17:44:00
> sessionInfo()R version 2.9.2 Patched (2009-09-24 r50069)
i386-pc-mingw32

locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
States.1252;LC_MONETARY=English_United
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252

attached base packages:
[1] stats     graphics  utils     datasets  grDevices methods  
base>
Vitalie.


=====================
  I would agree that this is a bug ... this patch gets rid of the error,
but leaves the labels very ugly -- given enough hours I might be able to
figure out how to make the labels nice, but someone else can probably do
it quicker (see comments in code below)


  It would probably also be worth adding something like

cut(Dates,2)

  around line 5067 of reg-tests-1.R


--- datetime.R	2009-10-15 13:01:15.000000000 -0400
***************
*** 764,770 ****
        }
      } else stop("invalid specification of 'breaks'")
      res <- cut(unclass(x), unclass(breaks), labels = labels, right right,
...)
!     if(is.null(labels)) levels(res) <-
as.character(breaks[-length(breaks)])
      res
  }

--- 764,782 ----
        }
      } else stop("invalid specification of 'breaks'")
      res <- cut(unclass(x), unclass(breaks), labels = labels, right right,
...)
!     if(is.null(labels)) {
!       if (is.numeric(breaks) && length(breaks) == 1L)
!         levels(res) <- as.character(breaks[-length(breaks)])
!       } else {
!         ## ?? what should happen here?
!         ## this version simply leaves the break values
!         ## as numeric (and very ugly)
!         ## I don't know how to safely convert the breakpoints
!         ## back to a character format (e.g.
!         ## levels(res) = [1970-01-01 00:00:00,1970-01-01 12:00:00)
!         ## instead of [18000,61200)
!       }
!     }
      res
  }


-- 
Ben Bolker
Associate professor, Biology Dep't, Univ. of Florida
bolker at ufl.edu / www.zoology.ufl.edu/bolker
GPG key: www.zoology.ufl.edu/bolker/benbolker-publickey.asc

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Ben Bolker

2009-Oct-16 14:12 UTC

head link

[Rd] forwarded: bug (?) in cut.POSIXt with "breaks"=integer

PS a parallel problem seems to occur in cut.Date  ... cut.POSIXt and cut.Date
both allow
breaks to be a single integer specifying the number of breaks, and both call

 if(is.null(labels)) levels(res) <- as.character(breaks[-length(breaks)])
  
near the end of the function, which breaks (so to speak) if
length(breaks)!=length(levels(res))-1

I could keep working on a patch if requested, but probably won't otherwise.

  Ben Bolker






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Gabor Grothendieck

2009-Oct-17 14:35 UTC

head link

[Rd] forwarded: bug (?) in cut.POSIXt with "breaks"=integer

That is usually done with trunc rather than cut since in the case of a
time series we normally don't want a factor result (which is what cut
would give):

trunc(tt, "secs")
trunc(tt, "mins")
# etc

trunc.POSIXt does not support the "30 secs" syntax but trunc.times in
the chron package supports similar functionality:

library(chron)
trunc(as.chron(format(tt)), "00:00:30")

# or relative to GMT
trunc(as.chron(tt)), "00:00:30")

On Thu, Oct 15, 2009 at 1:10 PM, Ben Bolker <bolker at ufl.edu>
wrote:>
> From: Vitalie S. <vitosmail <at> rambler.ru>
> Subject: Bug in cut.POSIXt
> Newsgroups: gmane.comp.lang.r.general
> Date: 2009-10-15 15:47:48 GMT (1 hour and 29 minutes ago)
>
> Hello Everyone,
>
> Before reporting decided to post here first:
>
> tt <- structure(c(1254238817, 1254238859, 1254238969, 1254239080), class
> c("POSIXt",
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
?"POSIXct"),
> tzone = "")
>
> cut.POSIXt(tt, 2)
> #Error in `levels<-.factor`(`*tmp*`, value = character(0)) :
> # ?number of levels differs
>
> cut.POSIXt(tt, 2, labels=c("a1", "a2"))
> #[1] a1 a1 a2 a2
> #Levels: a1 a2
>
> cut(tt, "2 mins")
> #[1] 2009-09-29 17:40:00 2009-09-29 17:40:00 2009-09-29 17:42:00
> 2009-09-29 17:44:00
> #Levels: 2009-09-29 17:40:00 2009-09-29 17:42:00 2009-09-29 17:44:00
>
>> sessionInfo()
> R version 2.9.2 Patched (2009-09-24 r50069)
> i386-pc-mingw32
>
> locale:
> LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
> States.1252;LC_MONETARY=English_United
> States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252
>
> attached base packages:
> [1] stats ? ? graphics ?utils ? ? datasets ?grDevices methods ? base
>>
>
> Vitalie.
>
>
> =====================>
> ?I would agree that this is a bug ... this patch gets rid of the error,
> but leaves the labels very ugly -- given enough hours I might be able to
> figure out how to make the labels nice, but someone else can probably do
> it quicker (see comments in code below)
>
>
> ?It would probably also be worth adding something like
>
> cut(Dates,2)
>
> ?around line 5067 of reg-tests-1.R
>
>
> --- datetime.R ?2009-10-15 13:01:15.000000000 -0400
> ***************
> *** 764,770 ****
> ? ? ? ?}
> ? ? ?} else stop("invalid specification of 'breaks'")
> ? ? ?res <- cut(unclass(x), unclass(breaks), labels = labels, right >
right, ...)
> ! ? ? if(is.null(labels)) levels(res) <-
> as.character(breaks[-length(breaks)])
> ? ? ?res
> ?}
>
> --- 764,782 ----
> ? ? ? ?}
> ? ? ?} else stop("invalid specification of 'breaks'")
> ? ? ?res <- cut(unclass(x), unclass(breaks), labels = labels, right >
right, ...)
> ! ? ? if(is.null(labels)) {
> ! ? ? ? if (is.numeric(breaks) && length(breaks) == 1L)
> ! ? ? ? ? levels(res) <- as.character(breaks[-length(breaks)])
> ! ? ? ? } else {
> ! ? ? ? ? ## ?? what should happen here?
> ! ? ? ? ? ## this version simply leaves the break values
> ! ? ? ? ? ## as numeric (and very ugly)
> ! ? ? ? ? ## I don't know how to safely convert the breakpoints
> ! ? ? ? ? ## back to a character format (e.g.
> ! ? ? ? ? ## levels(res) = [1970-01-01 00:00:00,1970-01-01 12:00:00)
> ! ? ? ? ? ## instead of [18000,61200)
> ! ? ? ? }
> ! ? ? }
> ? ? ?res
> ?}
>
>
> --
> Ben Bolker
> Associate professor, Biology Dep't, Univ. of Florida
> bolker at ufl.edu / www.zoology.ufl.edu/bolker
> GPG key: www.zoology.ufl.edu/bolker/benbolker-publickey.asc
>
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
>

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