[BioC] Rgraphviz: adding weight to an edge

[Li Long]

> Hi Li,
>
> It has to do with the sp.between function.
> Here is the thread where I reported the bug:
> https://stat.ethz.ch/pipermail/bioconductor/2005-November/011066.html
>
> Hope that helps,
> Adrien
>

Hi, Adrien,

Sorry that I missed the previous email bug report.

The function, sp.between, only handles graphs with non-negative weights.  It
should return error in your case instead of core-dumping.

I'll put in some checking and update the doc.

Thanks,

Li