Using R in RapidMiner

I installed the Execute R script operator in RapidMIner. Everything works fine but I found the following code didn't work:

rm_main = function(dataset)
{
    new_dataset = dataset[1,c(1,5)]
    return new_dataset
}

Basically all the operations using "[]"  doesn't work properly. I understand this can be done by Select Attributes in RapidMIner, but is it my problem or such R syntax is not supported in RapidMIner?