[R] melt in reshape2 destroying dates?

[John Kane]

Amazingly enough I think i actually understand that albeit superficially.
Thanks

John Kane
Kingston ON Canada


> -----Original Message-----
> From: smartpink111 at yahoo.com
> Sent: Mon, 13 May 2013 11:22:35 -0700 (PDT)
> To: jrkrideau at inbox.com
> Subject: Re: [R] melt in reshape2 destroying dates?
> 
> Hi John,
> No problem
> 
> If you look at the storage mode:
> storage.mode(mydata$dd1)
> #[1] "integer"
> 
> I think during melt, it
> class(mdat$value)
> #[1] "numeric"
>  class(mydata$dd1)
> #[1] "POSIXct" "POSIXt"
> I guess during melting, this gets coerced to integer class.
> You can also do:
>  mdat$value<-structure(mdat$value,class=c("POSIXt","POSIXct"))
> #or
> as.POSIXct(mdat$value,origin="1970-01-01")
> 
> class(mdat$value)
> #[1] "POSIXt"  "POSIXct"
> A.K.
> 
> 
> ----- Original Message -----
> From: John Kane <jrkrideau at inbox.com>
> To: arun <smartpink111 at yahoo.com>
> Cc: R help <r-help at r-project.org>
> Sent: Monday, May 13, 2013 2:11 PM
> Subject: Re: [R] melt in reshape2 destroying dates?
> 
> Thanks very much.   I could have sworn I had tried that but obviously I
> had not.
> 
> So melt() is returning the correct value which is what I had suspected
> but I obiously did not convert it properly.I wonder if this buggy enough
> to mention the behaviour to the package maintainer?
> 
> 
> 
> John Kane
> Kingston ON Canada
> 
> 
>> -----Original Message-----
>> From: smartpink111 at yahoo.com
>> Sent: Mon, 13 May 2013 11:05:58 -0700 (PDT)
>> To: jrkrideau at inbox.com
>> Subject: Re: [R] melt in reshape2 destroying dates?
>> 
>> In the first case:
>>  mdat$value<-.POSIXct(mdat$value,tz="EST")
>>  mdat$value[1:3]
>> #[1] "2012-01-01 01:00:00 EST" "2012-01-01 02:00:00 EST"
>> #[3] "2012-01-01 03:00:00 EST"
>>  mydata$dd1[1:3]
>> #[1] "2012-01-01 01:00:00 EST" "2012-01-01 02:00:00 EST"
>> #[3] "2012-01-01 03:00:00 EST"
>> A.K.
>> 
>> 
>> 
>> ----- Original Message -----
>> From: John Kane <jrkrideau at inbox.com>
>> To: r-help at r-project.org
>> Cc:
>> Sent: Monday, May 13, 2013 1:36 PM
>> Subject: [R] melt in reshape2 destroying dates?
>> 
>> When I melt a data frame with some dates I am getting some strange
>> results. I seem to lose the date format with POSIXct and get a row of
>> zeros with POSIXlt
>> 
>> Any suggestions as to what I am messing up? Code and data below.
>> Thanks,
>> John Kane
>> Kingston ON Canada
>> 
>> mydata  <-  structure(list(dd1 = structure(c(1325397600L, 1325401200L,
>> 1325404800L,
>> 1325408400L, 1325412000L, 1325415600L, 1325419200L, 1325422800L,
>> 1325426400L, 1325430000L, 1325433600L, 1325437200L, 1325440800L,
>> 1325444400L, 1325448000L, 1325451600L, 1325455200L, 1325458800L,
>> 1325462400L, 1325466000L), class = c("POSIXct", "POSIXt"), tzone = ""),
>>     dd2 = structure(c(1325426400, 1325412000, 1325426400, 1325422800,
>>     1325422800, 1325426400, 1325433600, 1325437200, 1325455200,
>>     1325458800, 1325451600, 1325458800, 1325466000, 1325466000,
>>     1325476800, 1325476800, 1325480400, 1325466000, 1325480400,
>>     1325491200), class = c("POSIXct", "POSIXt"), tzone = ""),
>>     emp = structure(c(1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L,
>>     1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L), class = "factor", .Label =
>> c("part-time",
>>     "self-employed")), period = 1:20), .Names = c("dd1", "dd2",
>> "emp", "period"), row.names = c(NA, -20L), class = "data.frame")
>> 
>> library(lubridate)
>> library(reshape2)
>> 
>>   str(mydata)
>>   mdat  <-  melt(mydata, id=c("emp","period"))
>>   str(mdat)
>> 
>>   # alternatively
>> 
>>   mydata$dd1  <-  as.POSIXlt(mydata$dd1)
>>   mydata$dd2  <-  as.POSIXlt(mydata$dd2)
>>   str(mydata)
>>   mdat  <-  melt(mydata, id=c("emp","period"))
>>   str(mdat)
>> 
>> ____________________________________________________________
>> TRY FREE IM TOOLPACK at http://www.imtoolpack.com/default.aspx?rc=if5
>> Capture screenshots, upload images, edit and send them to your friends
>> through IMs, post on Twitter®, Facebook®, MySpace™, LinkedIn® – FAST!
>> 
>> ______________________________________________
>> R-help at 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.
> 
> ____________________________________________________________
> FREE 3D MARINE AQUARIUM SCREENSAVER - Watch dolphins, sharks & orcas on
> your desktop!
> Check it out at http://www.inbox.com/marineaquarium

____________________________________________________________
FREE ONLINE PHOTOSHARING - Share your photos online with your friends and family!
Visit http://www.inbox.com/photosharing to find out more!