Thanks for your reply. Below is the sessionInfo():
R version 3.5.1 (2018-07-02)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS 10.14.2
Matrix products: default
BLAS: /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
LAPACK: /Library/Frameworks/R.framework/Versions/3.5/Resources/lib/libRlapack.dylib
locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] compiler_3.5.1 bookdown_0.8 htmltools_0.3.6 tools_3.5.1 yaml_2.2.0 Rcpp_1.0.0 rmarkdown_1.11 blogdown_0.9
[9] knitr_1.21 xfun_0.4 digest_0.6.18 packrat_0.5.0 evaluate_0.12
I am using a third party Chinese IME, but I also tried the default system Chinese IME (Pinyin - Simplified), it has the same issue.