Best way to check/assert a certain version of [R] or a package

[Prof Brian D Ripley]

On Thu, 24 Jan 2002, Thomas Lumley wrote:

> On Fri, 25 Jan 2002, Henrik Bengtsson wrote:
>
> > When loading a package with library(APkg) or require(APkg) I would like to
> > make sure that (1) the correct version of [R] is installed. If not an
> > informative error message should be given. I would also like to make sure
> > that (2)  another required package which is loaded from within the APkg
> > package (by require(OtherPkg)) is of a certain version or later.
>
> Following my usual habit of answering a different question from the one
> you asked: there is an automated way to do this at install-time, which
> should be sufficient for requiring 'at least' a certain version.  The `Depends'
> field in the DESCRIPTION is described in `Writing R Extensions'

I don't think it is sufficient, and have been about to propose automatic
run-time R version checking.  The problem is that if installed on one
version it can be used on another.  It's a particular problem with binary
distributions.


> > First of all, I believe that the check should be done in .First.lib(),
> > correct? To check for the correct version of [R] I would guess that
> > R.Version()$major and R.Version()$minor could be used to retrieve the
> > version. Is there any prewritten function to compare two version strings;
> > "1.2.1" is before "1.2.10"?
>
>  No, but you can convert it to a vector of numbers with
> eg as.numeric(strsplit("1.2.10","\\.")[[1]])
> and compare the resulting numbers

Yes, but for checking R versions that does not arise.

R.Version()$major == 1 && R.Version()$minor >= 4.1

will work (and normally >= 4 is the sort of test required).

> > What is the easiest way to retrieve the version string of a certain package.
> > Should one find the path to the package, then load the DESCRIPTION file and
> > parse it?
>
> eg
> > read.dcf(file = system.file("DESCRIPTION",package="MASS"),fields="Version")
>      Version
> [1,] "6.3-2"
>
>
> 	-thomas
>
>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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