r - Rscript could not find function

Question

I need to run several scripts via the bash shell using Rscript and some functions I use require the function isGeneric. However, in this case the process end like that (for example):

Error in .getLogLik() : could not 
find function "isGeneric"
Calls: main -> dredge -> .getLik -> .getLogLik
Execution halted

This can be reproduced as follows

# in the bash shell
echo "isGeneric('apply')" > /tmp/test.R
Rscript /tmp/test.R

Result:

Error: could not find function "isGeneric"
Execution halted

However, if we open a R session and type the following, it works:

# in the R shell
isGeneric('apply')
[1] FALSE

Would you know where the problem comes from and how to fix it?

Answer 1

According to help(Rscript), Rscript doesn't load the methods package by default, because it's time-consuming. So you either need to specify it on the command line:

Rscript --default-packages=methods file.R

Or library(methods) at the top of the file you're calling.