During startup - Warning messages:
1: Setting LC_CTYPE failed, using "C"
2: Setting LC_COLLATE failed, using "C"
3: Setting LC_TIME failed, using "C"
4: Setting LC_MESSAGES failed, using "C"
5: Setting LC_PAPER failed, using "C"
というメッセージが表示される場合は，ターミナルにて
defaults write org.R-project.R force.LANG en_US.UTF-8
を実行します．
