I can load the xlsx package in R or RStudio, ,but when I can't use it inside KNIME. I've installed the R package xlsx using "install.packages(xlsx)" within R snippet including the dependencies, but when I run "library(xlsx)", I get the error below.
Error : .onAttach failed in attachNamespace() for 'xlsx', details:
call: .jcall("java.lang.System", "S", "getProperty", "java.version")
error: RcallMethod: cannot determine object class
Error: package or namespace load failed for 'xlsx'
I think that this post (second solution on the page) should solve your problem: https://orajavasolutions.wordpress.com/2014/06/03/installing-and-loading-xlsx-package-in-r-with-ubuntu/