[R] xts conversion problem

David Winsemius dwinsemius at comcast.net
Thu Nov 12 23:01:29 CET 2009


Looks as though str does not expose a sufficient amount of hte  
attributes of these objects to fully explain the differences. Why not  
post the results of dput on both objects?

-- 
David

On Nov 12, 2009, at 2:18 PM, Nandi wrote:

> I have two data frames, with two columns each, the first being a Date
> variable. I would like to convert them to xts objects, indexed by the
> Date column. I would like to use as.Date and not as.POSIXct as the
> dateformat. The puzzling fact is that it works for the first one but
> not the other. Here is a screenshot of the error:
>
>> str(DF1)
> 'data.frame':   367 obs. of  2 variables:
> $ Date:Class 'Date'  num [1:367] 13515 13516 13517 13518 13521 ...
> $ X   : num  28.29 -53.58 58.33 -23.07 9.73 ...
>> str(DF2)
> 'data.frame':   322 obs. of  2 variables:
> $ Date:Class 'Date'  num [1:322] 14061 14062 14063 14067 14068 ...
> $ X   : num  56.9 -16.6 50.1 -17.8 18.6 ...
>> DF1.xts <- as.xts(DF1, order.by=as.Date(DF1$Date))
> Warning messages:
> 1: In structure(.Internal(as.POSIXct(x, tz)), class = c("POSIXt",
> "POSIXct"),  :
>  unknown timezone 'merica/Chicago'
> 2: In structure(.Internal(as.POSIXct(x, tz)), class = c("POSIXt",
> "POSIXct"),  :
>  unknown timezone 'merica/Chicago'
> 3: In structure(.Internal(as.POSIXct(x, tz)), class = c("POSIXt",
> "POSIXct"),  :
>  unknown timezone 'merica/Chicago'
> 4: In structure(.Internal(as.POSIXct(x, tz)), class = c("POSIXt",
> "POSIXct"),  :
>  unknown timezone 'merica/Chicago'
> 5: In structure(.Internal(as.POSIXct(x, tz)), class = c("POSIXt",
> "POSIXct"),  :
>  unknown timezone 'merica/Chicago'
>> DF2.xts <- as.xts(DF2, order.by=as.Date(DF2$Date))
> Error in as.POSIXlt.character(x, tz, ...) :
>  character string is not in a standard unambiguous format
>
> I am using R2.10.0, and the latest version of xts (see below). I would
> like to understand the cause of this error. I have been experiencing
> pretty random errors with the latest version of R & xts. I was
> wondering if anyone else is having similar issues. Thanks a lot.
>
>> version
>              _
> platform       i386-pc-mingw32
> arch           i386
> os             mingw32
> system         i386, mingw32
> status
> major          2
> minor          10.0
> year           2009
> month          10
> day            26
> svn rev        50208
> language       R
> version.string R version 2.10.0 (2009-10-26)
>> packageDescription(pkg='xts')
> Package: xts
> Type: Package
> Title: Extensible Time Series
> Version: 0.6-9
> Date: 2009-10-14
> Author: Jeffrey A. Ryan, Josh M. Ulrich
> Depends: zoo
> Suggests: timeSeries,timeDate,tseries,its,chron,fts,tis
> LazyLoad: yes
> Maintainer: Jeffrey A. Ryan <jeff.a.ryan at gmail.com>
> Description: Provide for uniform handling of R's different time-based
> data
>        classes by extending zoo, maximizing native format information
>        preservation and allowing for user level customization and
>        extension, while simplifying cross-class interoperability.
> License: GPL-3
> URL: http://r-forge.r-project.org/projects/xts/
> Repository: R-Forge
> Repository/R-Forge/Project: xts
> Repository/R-Forge/Revision: 463
> Date/Publication: 2009-11-06 17:56:20
> Packaged: 2009-11-06 21:12:13 UTC; rforge
> Built: R 2.10.0; i386-pc-mingw32; 2009-11-11 00:09:42 UTC; windows
>
> -- File: C:/PROGRA~1/R/R-210~1.0/library/xts/Meta/package.rds
>
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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.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT



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