[Rd] particulars of importing/loading libraries

[Martin Morgan]

Hi Oleg --

"Sklyar, Oleg (London)" <osklyar at maninvestments.com> writes:

> 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?

I think that exportPattern does a simple ls() on the environment of
the package name space. The imported symbols are not defined in that
environment, but (I think) in a variable .__NAMESPACE__. and so are
not discovered.  Arguably, exportPattern (and friends) should be
smarter. Pragmatically, you need to re-export imported symbols
explicitly. I haven't worked this through entirely, and could be
wrong...

Martin

> 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).
>
> 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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-- 
Martin Morgan
Computational Biology / Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N.
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