R help - Jan 2002 - Best way to check/assert a certain version of or a package

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.

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"?
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?

Thanks a lot

Henrik Bengtsson

Dept. of Mathematical Statistics @ Centre for Mathematical Sciences
Lund Institute of Technology/Lund University, Sweden (+2h UTC)
Office: P316, +46 46 222 9611 (phone), +46 46 222 4623 (fax)
h b @ m a t h s . l t h . s e
http://www.maths.lth.se/matstat/staff/hb/


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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'
> 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
> 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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On Fri, 25 Jan 2002, Henrik Bengtsson wrote:

[...]
> 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?
Take a look at packageStatus, which uses package.description and
compareVersion.  package.dependencies can be used to test the R version
at present, at least.

-- 
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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Thanks for all you replies here. Here is a short summary how to solve the
two problems discussed:

1) Check for correct version of [R]

  current <- paste(R.Version()[c("major", "minor")],
collapse=".")
  wanted <- "1.4.0"
  tooOld <- (compareVersion(current, wanted) < 0)

2) Check for correct version of a package

  package <- "eda"
  current <- package.description(package)["Version"]
  wanted <- "1.3.1"
  tooOld <- (compareVersion(current, wanted) < 0)

It could be questioned if compareVersion("1.4.0", "1.4")
should give 1
and not 0, but hopefully that is not an real issue.

PS. packageStatus() seems promising. DS.

Have nice day!

Henrik Bengtsson

Dept. of Mathematical Statistics @ Centre for Mathematical Sciences 
Lund Institute of Technology/Lund University, Sweden (+2h UTC)
Office: P316, +46 46 222 9611 (phone), +46 46 222 4623 (fax)
h b @ m a t h s . l t h . s e
http://www.maths.lth.se/matstat/staff/hb/



On Fri, 25 Jan 2002, Prof Brian Ripley wrote:
> On Fri, 25 Jan 2002, Henrik Bengtsson wrote:
> 
> [...]
> 
> > 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?
> 
> Take a look at packageStatus, which uses package.description and
> compareVersion.  package.dependencies can be used to test the R version
> at present, at least.
> 
> -- 
> 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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