[R] checking if a package is installed

[David Winsemius]

On Aug 26, 2010, at 9:07 PM, pdb wrote:

>
> Hi,
>
> I am writing a function that requires a specific package to be  
> installed.
>
> Is there a way of checking if the package is installed and returning  
> a TRUE
> / FALSE result so my function can return an appropriate error  
> message and
> exit the function gracefully rather than just bombing out?
>
> I'm thinking along the following lines (but want code that works),
>
> f_checkpackage <- function()
> {
>
> if (library(madeupname) == TRUE) {

You don't need the ==TRUE

 > if ( require(rms) ) {TRUE}
[1] TRUE

 > if ( require(beanplot) ) {TRUE} else {FALSE}
Loading required package: beanplot
[1] FALSE
Warning message:
In library(package, lib.loc = lib.loc, character.only = TRUE,  
logical.return = TRUE,  :
   there is no package called 'beanplot'

According to the library/require help page library can be cajoled into  
returning a logical vlaue if you tell it: logical.return = TRUE
.
-- 
David.


>

>  cat("package loaded OK\n")
> }
> else
> {
>     cat("ERROR: package not loaded")
> }
>
> }
>
> f_checkpackage()
> -- 
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> Sent from the R help mailing list archive at Nabble.com.
>
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David Winsemius, MD
West Hartford, CT