[R] determining if a function exists in a particular package

[William Dunlap]

> I looked at exists and objects, but they seem to refer to an
> environment rather than a package.

Those functions work with the names of attached packages, but you have
know that the name of an attached package has "package:" prefixed to
the package's usual name.  E.g.,
  > exists("lm", "package:stats")
  [1] TRUE
  > objects("package:stats", pattern="iso")
  [1] "isoreg"
If you leave off the "package:" you might be misled into thinking an
environment is required:
  > objects("stats", pattern="iso")
  Error in as.environment(pos) : no item called "stats" on the search list

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Erin Hodgess
> Sent: Friday, April 27, 2012 2:08 PM
> To: R help
> Subject: [R] determining if a function exists in a particular package
> 
> Hello R People:
> 
> Is there a way to determine if a function exists in a particular
> package, please?
> 
> I looked at exists and objects, but they seem to refer to an
> environment rather than a package.
> 
> I was thinking of something like:
> 
> ifelse(exists(functiona) in MASS, print(1:10), print(5))
> 
> Thanks,
> Erin
> 
> 
> --
> Erin Hodgess
> Associate Professor
> Department of Computer and Mathematical Sciences
> University of Houston - Downtown
> mailto: erinm.hodgess at gmail.com
> 
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