On May 23, 2013, at 7:56 PM, arun wrote:
> I guess it is due to vectorization.
The concept of "vectorization" is much broader than the activities of
`as.vector`, but it needs a specific functional mechanism to be considered an
explanation.
> vec1<- as.Date(Data[,2],origin="1899-12-30")
> class(vec1)
> #[1] "Date"
> as.vector(vec1)
> # [1] 15758 15765 15772 15779 NA 15793 15800 15807 NA 15821 15828
It is certainly true that `as.vector` could unclass a Date-classed vector, but
why do you believe this has anything to do with how `$<-` returns its
functional result? Setting `trace` on `as.vector` does not result in any signal
suggesting that it was called:
> trace('as.vector')
> Data$Dat1b = as.Date(Data[ ,"dat1"], origin="1899-12-30")
# Nothing
> trace( .Primitive("$<-") )
> Data$Dat1b = as.Date(Data[ ,"dat1"], origin="1899-12-30")
trace: `$<-`(`*tmp*`, Dat1b, value = c(15758, 15765, 15772, 15779, 15786,
15793, 15800, 15807, 15814, 15821, 15828))
>
> head(as.list(vec1),2)
> #[[1]]
> #[1] "2013-02-22"
> #
> #[[2]]
> #[1] "2013-03-01"
> head(data.frame(vec1),2)
> # vec1
> #1 2013-02-22
> #2 2013-03-01
>
>
> unlist(as.list(vec1))
> # [1] 15758 15765 15772 15779 NA 15793 15800 15807 NA 15821 15828
>
>
> Also, please check:
>
> http://r.789695.n4.nabble.com/as-vector-with-mode-quot-list-quot-and-POSIXct-td4667533.html
Interesting but I fail to see the connection to this instance other than R
behaving somewhat differently than we might at one time have expected.
--
David.
>
> A.K.
>
> ----- Original Message -----
> From: Denis Chabot <chabot.de...@gmail.com>
> To: arun <smartpink...@yahoo.com>
> Cc: R help <r-help@r-project.org>
> Sent: Thursday, May 23, 2013 10:06 PM
> Subject: Re: [R] subsetting and Dates
>
> Thank you for the 2 methods to make the columns class Date, but I would
> really like to know why these variables were not in Date class with my code.
> Do you know?
>
> Denis
>
>
> Le 2013-05-23 à 21:44, arun <smartpink...@yahoo.com> a écrit :
>
>> You could convert those columns to "Date" class by:
>>
>>
>> Data[,c(4,6)]<-lapply(Data[,c(4,6)],as.Date,origin="1970-01-01")
>> #or
>> Data[,c(4,6)]<-lapply(Data[,c(4,6)],function(x) structure(x,class="Date"))
>>
>>
>> # dat1 dat2 Dat1a Dat1b Dat2a Dat2b
>> #1 41327 41327 2013-02-22 2013-02-22 2013-02-22 2013-02-22
>> #2 41334 41334 2013-03-01 2013-03-01 2013-03-01 2013-03-01
>> #3 41341 41341 2013-03-08 2013-03-08 2013-03-08 2013-03-08
>> #4 41348 41348 2013-03-15 2013-03-15 2013-03-15 2013-03-15
>> #5 41355 NA 2013-03-22 2013-03-22 <NA> <NA>
>> #6 41362 41362 2013-03-29 2013-03-29 2013-03-29 2013-03-29
>> #7 41369 41369 2013-04-05 2013-04-05 2013-04-05 2013-04-05
>> #8 41376 41376 2013-04-12 2013-04-12 2013-04-12 2013-04-12
>> #9 41383 NA 2013-04-19 2013-04-19 <NA> <NA>
>> #10 41390 41390 2013-04-26 2013-04-26 2013-04-26 2013-04-26
>> #11 41397 41397 2013-05-03 2013-05-03 2013-05-03 2013-05-03
>> A.K.
>>
>> ----- Original Message -----
>> From: Denis Chabot <chabot.de...@gmail.com>
>> To: R-help@r-project.org
>> Cc:
>> Sent: Thursday, May 23, 2013 5:35 PM
>> Subject: [R] subsetting and Dates
>>
>> Hi,
>>
>> I am trying to understand why creating Date variables does not work if I
>> subset to avoid NAs.
>>
>> I had problems creating these Date variables in my code and I thought that
>> the presence of NAs was the cause. So I used a condition to avoid NAs.
>>
>> It turns out that NAs are not a problem and I do not need to subset, but I'd
>> like to understand why subsetting causes the problem.
>> The strange numbers I start with are what I get when I read an Excel sheet
>> with the function read.xls() from package gdata.
>>
>> dat1 = c(41327, 41334, 41341, 41348, 41355, 41362, 41369, 41376, 41383,
>> 41390, 41397)
>> dat2 = dat1
>> dat2[c(5,9)]=NA
>> Data = data.frame(dat1,dat2)
>>
>> keep1 = !is.na(Data$dat1)
>> keep2 = !is.na(Data$dat2)
>>
>>
>> Data$Dat1a = as.Date(Data[,"dat1"], origin="1899-12-30")
>> Data$Dat1b[keep1] = as.Date(Data[keep1,"dat1"], origin="1899-12-30")
>> Data$Dat2a = as.Date(Data[,"dat2"], origin="1899-12-30")
>> Data$Dat2b[keep2] = as.Date(Data[keep2,"dat2"], origin="1899-12-30")
>>
>> Data
>> dat1 dat2 Dat1a Dat1b Dat2a Dat2b
>> 1 41327 41327 2013-02-22 15758 2013-02-22 15758
>> 2 41334 41334 2013-03-01 15765 2013-03-01 15765
>> 3 41341 41341 2013-03-08 15772 2013-03-08 15772
>> 4 41348 41348 2013-03-15 15779 2013-03-15 15779
>> 5 41355 NA 2013-03-22 15786 <NA> NA
>> 6 41362 41362 2013-03-29 15793 2013-03-29 15793
>> 7 41369 41369 2013-04-05 15800 2013-04-05 15800
>> 8 41376 41376 2013-04-12 15807 2013-04-12 15807
>> 9 41383 NA 2013-04-19 15814 <NA> NA
>> 10 41390 41390 2013-04-26 15821 2013-04-26 15821
>> 11 41397 41397 2013-05-03 15828 2013-05-03 15828
>>
>> So variables Dat1b and Dat2b are not converted to Date class.
>>
>>
>> sessionInfo()
>> R version 2.15.2 (2012-10-26)
>> Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)
>>
>> locale:
>> [1] fr_CA.UTF-8/fr_CA.UTF-8/fr_CA.UTF-8/C/fr_CA.UTF-8/fr_CA.UTF-8
>>
>> attached base packages:
>> [1] stats graphics grDevices utils datasets methods base
>>
>> other attached packages:
>> [1] gdata_2.12.0
>>
>> loaded via a namespace (and not attached):
>> [1] gtools_2.7.0
>>
>> Thanks in advance,
>>
>> Denis
>> ______________________________________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius
Alameda, CA, USA
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
