[R] How can I check a package is installed or not?

[David Winsemius]

On Sep 27, 2011, at 3:19 PM, Fabrice Tourre wrote:

> Dear list,
>
> How can I detect a package is installed or not? If not, then install  
> it.
>
> For example, in a script, I want to check the package DESeq is
> installed or not. If not, then I will using this script to install it.
>
> source("http://www.bioconductor.org/biocLite.R")
> biocLite("DESeq")
>
> The pseudo script would be like this:
>
> try:
>    library(

Perhaps:

if ( require("DESeq") ) {  do-stuff } else {
                source("http://www.bioconductor.org/biocLite.R")
                biocLite("DESeq") }

'require' reports success or failure with a logical and loads the  
package if successful. You need to add logical.return=TRUE to a  
'library' call to get avoid getting a character value back.

> catch:
>    source("http://www.bioconductor.org/biocLite.R")
>    biocLite("DESeq")
>
> Thank you
>
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David Winsemius, MD
West Hartford, CT