[Rd] particulars of importing/loading libraries

[Simon Urbanek]

Oleg,

On Jan 13, 2009, at 11:00 , Sklyar, Oleg (London) wrote:

> Dear List:
>
> Sorry for posting maybe a trivial question, but I have a basic
> understanding problem. If I have say pack1 and pack2, two R packages,
> and pack2 depends on and imports pack1 fully (as in the code below),  
> is
> there a way to make all the functionality of pack1 available for the
> global and other environments (not only for the functions called from
> withing pack2) by loading pack2 only? I thought if pack2 depends on  
> and
> imports pack1 and essentially reexports everything, one should get the
> full functionality simply by loading pack2. This does not seem to be  
> the
> case or I am missing something trivial in my NAMESPACE/DESCRIPTION
> files?
>
> If this is documented in Writing R Extensions, I would be thankful  
> for a
> page number and maybe a quick fix in my example below as so far I have
> not been able to find a clear explanation.
>
> The problem can be illustrated by the following simple example (this  
> is
> a simple code for 2 packages, pack1 and pack2; plus an example).
>

if you bothered to use R CMD check you would find your bug right away:
* checking package dependencies ... ERROR
Namespace dependencies not required:
   pack1

You simply forgot to add pack1 to the Depends: line - that's all. Once  
you fix that, you'll see what happens:

 > library(pack2)
Loading required package: pack1
 > as.POSIXct(pack1::testPosixVal)
[1] "2009-01-14 01:38:08 UTC"

Cheers,
S


> Thank you for your replies.
>
> Dr Oleg Sklyar
> Research Technologist
> AHL / Man Investments Ltd
> +44 (0)20 7144 3107
> osklyar at maninvestments.com
>
> --- pack1: DESCRIPTION ------
> Package: pack1
> Version: 0.0.1
> Date: 12 Jan 2009
> Title: pack1 to test S3/S4 methods compatibility
> Author:  Oleg Sklyar
> Depends: R (>= 2.7.1), methods
> Maintainer: Oleg Sklyar <osklyar at maninvestments.com>
> Description: pack1
> LazyLoad: yes
> License: Proprietary
> URL: http://www.maninvestments.com
> LazyLoad: no
>
> --- pack1: NAMESPACE ------
> import(methods)
> exportPattern("^[^\\.]")
> exportClasses(posixTime)
> exportMethods(as.POSIXct)
>
> --- pack1: posix.R ------
> setClass("posixTime", "numeric")
>
> setGeneric("as.POSIXct")
> setMethod("as.POSIXct", signature(x="posixTime"),
>    function(x, tz) {
>        z = x at .Data
>        attr(z,"class") = c("POSIXt", "POSIXct")
>        attr(z,"tzone") = "UTC"
>        z
>    }
> )
>
> testPosixVal = new("posixTime", as.numeric(Sys.time()))
>
> --- pack2: DESCRIPTION
> Package: pack2
> Version: 0.0.1
> Date: 12 Jan 2009
> Title: pack2 to test S3/S4 methods compatibility
> Author:  Oleg Sklyar
> Depends: R (>= 2.7.1), methods
> Maintainer: Oleg Sklyar <osklyar at maninvestments.com>
> Description: pack2
> LazyLoad: yes
> License: Proprietary
> URL: http://www.maninvestments.com
> LazyLoad: no
>
> --- pack2: NAMESPACE ------
> import(pack1)
> exportPattern("^[^\\.]")
>
> --- pack2: posix.R ------
> testPosix = function() {
>    z = as.POSIXct(testPosixVal)
>    print(z)
>    print(class(z))
>    z
> }
>
> ------ test code to run from global env, showing problems -------
> require(pack2)
>
> ## use as.POSIXct imported into pack2 from pack1 to do the  
> conversion in
> the fun
> testPosix()
> #~ [1] "2009-01-13 15:29:50 UTC"
> #~ [1] "POSIXt"  "POSIXct"
> #~ [1] "2009-01-13 15:29:50 UTC"
>
> ## now try using it directly from the global env (pack1 was not
> explicitly loaded)
> as.POSIXct(pack1::testPosixVal)
> #~ Error in as.POSIXct.default(pack1::testPosixVal) :
> #~  do not know how to convert 'pack1::testPosixVal' to class  
> "POSIXlt"
>
> ## now require pack1 explicitly and try again
> require(pack1)
> as.POSIXct(pack1::testPosixVal)
> #~ [1] "2009-01-13 15:29:50 UTC"
>
>
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