[R] Checking if a library is loaded or not

[Prof Brian Ripley]

On Thu, 14 Sep 2000, Uwe Ligges wrote:

> Mark Myatt wrote:
> > 
> > How do I check if a library has already been loaded and then load it if
> > required?
> 
> To check, which libraries are loaded:
>  search()
> 
> 
> But you might want to use
>  require()

Actually, just library(foo) does exactly what is required, that is to
load the library if it is not already loaded.  require() checks for
the use of provide(), but that is deprecated now so require() is
really just a wrapper for library().

Brian

-- 
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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