require() is not giving TRUE / FALSE statements ?
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 G?nomique Int?gratives 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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