[R] require() is not giving TRUE / FALSE statements ?
Duncan Murdoch
murdoch at stats.uwo.ca
Tue Mar 10 21:30:04 CET 2009
On 10/03/2009 4:15 PM, Wolfgang Raffelsberger wrote:
> Dear list,
>
> ?require says :
> "... |require| is designed for use inside other functions; it returns
> |FALSE| and gives a warning (rather than an error as |library()| does by
> default) if the package does not exist ..."
>
> However when I run the following code I don't get any TRUE / FALSE
> statements (but the warning only).
You never printed the value, so you didn't see it. (It was returned
marked invisible, i.e. not for printing.)
Just save the value to a variable, or use it in a test, or explicitly
print it:
> print(require(stats))
[1] TRUE
> print(require(doesNotExist))
Loading required package: doesNotExist
[1] FALSE
Warning message:
In library(package, lib.loc = lib.loc, character.only = TRUE,
logical.return = TRUE, :
there is no package called 'doesNotExist'
Duncan Murdoch
> Since I want to test from inside of a function if a given package is
> installed (and do some specific actions like eg trying to install if the
> answer is negative), I need the FALSE statement for use with if(). I
> found a work-around (see below), but I wanted to bring to your attention
> that require() doesn't give the message(s) it's supposed to return.
>
> Wolfgang
>
> > require(stats)
> > require(doesNotExist) # example for library that's not
> existing on my system
> Loading required package: doesNotExist
> Warning message:
> In library(package, lib.loc = lib.loc, character.only = TRUE,
> logical.return = TRUE, :
> there is no package called 'doesNotExist'
>
> >## After all I found a work-around with :
> >library(doesNotExist,logical.return=T)
> [1] FALSE
> Warning message:
> In library(doesNotExist, logical.return = T) :
> there is no package called 'doesNotExist'
>
>
> >## for completeness :
> > sessionInfo()
> R version 2.8.1 (2008-12-22)
> i386-pc-mingw32
>
> locale:
> LC_COLLATE=French_France.1252;LC_CTYPE=French_France.1252;LC_MONETARY=French_France.1252;LC_NUMERIC=C;LC_TIME=French_France.1252
>
> attached base packages:
> [1] stats graphics grDevices datasets tcltk utils
> methods base
>
> other attached packages:
> [1] RODBC_1.2-4 svSocket_0.9-5 svIO_0.9-5 R2HTML_1.59
> svMisc_0.9-5 svIDE_0.9-5
>
> loaded via a namespace (and not attached):
> [1] tools_2.8.1
>
>
>
> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
> Wolfgang Raffelsberger, PhD
> Laboratoire de BioInformatique et Génomique Intégratives
> CNRS UMR7104, IGBMC
> 1 rue Laurent Fries, 67404 Illkirch Strasbourg, France
> Tel (+33) 388 65 3300 Fax (+33) 388 65 3276
> wolfgang.raffelsberger (at) igbmc.fr
>
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