Create the R session if it does not exist and returns its identifier.
See also
Other session functions:
opal.session_delete(),
opal.session_events(),
opal.session_exists(),
opal.session_get(),
opal.session_running()
Examples
if (FALSE) { # \dontrun{
o <- opal.login('administrator','password', url='https://opal-demo.obiba.org')
opal.session(o)
opal.logout(o)
} # }