swirl 課程安裝失敗

[KuiMing]

Installing swirl course for R basic...

| Course installation failed.

Installing swirl course for R ETL

| Course installation failed.

Installing swirl course for R Visualization

| Course installation failed.

There were 27 warnings (use warnings() to see them)

[wush978]

https://github.com/TaiwanRUserGroup/DSC2015Tutorial/wiki/Q&A#swirl-%E8%AA%B2%E7%A8%8B%E5%AE%89%E8%A3%9D%E5%A4%B1%E6%95%97