The installation of xlsx package seemed successful, but when I require it (using library) the following error comes up
Error: package or namespace load failed for ‘xlsx’:
.onLoad failed in loadNamespace() for 'rJava', details:
call: fun(libname, pkgname)
error: JAVA_HOME cannot be determined from the Registry
Do you have Java installed in your system? If so it matches the same architecture than R i.e. 64bit? Do you java rJava package installed? On which operating system are you?