Re: [R] How to build a package which loads Rgraphviz (if installed)...

From: William Revelle <>
Date: Sat, 12 Jul 2008 16:47:54 -0500

When I had an almost identical problem last year. I also wanted to use Rraphviz but only if people had it.

Kurt Hornik suggested that I replace a direct call to the function, foo, that uses Rgraphviz with

if(require("Rgraphviz")) foo()


At 10:23 PM +0200 7/12/08, Søren Højsgaard wrote:
>Dear List,
>I use Rgraphviz for display of graphs in some
>packages. Since Rgraphviz is no longer on CRAN
>it needs to be installed from Bioconductor and
>that is fine, but I have trouble figureing out
>the following: I create a plot method which - if
>Rgraphviz is installed - uses Rgraphviz for
>displaying and otherwise does nothing. This is
>implemented as:
> if (!("package:Rgraphviz" %in% search())){
> if("Rgraphviz" %in% installed.packages()){
> require(Rgraphviz)
> } else {
> cat("The Rgraphviz package (from
>Bioconductor) must be installed to display the
> return()
> }
> }
> ... else go on and do the plotting...
>When I run rcmd check packagename (on Windows XP, using R.2.7.1) I get
>* checking for unstated dependencies in R code ... WARNING
>'library' or 'require' calls not declared from:
> Rgraphviz
>See the information on DESCRIPTION files in the chapter 'Creating R
>packages' of the 'Writing R Extensions' manual.
>I can not state Rgraphviz in the Depends-field
>of the DESCRIPTION file because then the package
>does not pass the windows checks for going on
>CRAN. I can not see any solution from "writing R
>extensions", but I apologize if I have
>overlooked it. Does anyone have a suggestion on
>what to do?
> mailing list
>PLEASE do read the posting guide
>and provide commented, minimal, self-contained, reproducible code.

William Revelle
Department of Psychology   
Northwestern University
Attend  ISSID/ARP:2009     

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Received on Sat 12 Jul 2008 - 21:53:33 GMT

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