R tips and tricks

1) R.setenv() and R.getenv() can help you set environment variables for packages like rJava from within R.

syntax:

print(Sys.setenv(R_TEST="testit", "A+C"=123))  # `A+C` could also be used
Sys.getenv("R_TEST")
Sys.unsetenv("R_TEST")  # may warn and not succeed

2) R has no bound checking for lists or arrays, so one has to take care of it manually. For example:

arr[length(arr)+1] simply yeilds a NA
This becomes an issue in running for loops

for (i in (2:length(arr))) will not work out well if length(arr)<2