There are only two steps to add functionality of showing math formular in Jekyll. MathJax is the engine to achive it.
When updating R on Mac, we can uninstall the old version and install the new version. Uninstalling R is very easy on Mac.
I usually saw some tutorials in youtube about how to use softwares. There is a high probability that people in the video used Mac to teach how to program. In the past, I feel doubt that why it happened. Last year, in the thanksgiving’s shopping season ($150 off), I decided to buy 13 inch, not too big and heavy, not too small. In the store, it was easy for me to confuse which one to buy, Mac Pro or Mac Air. The employee in the NYU Mac store said price performance ratio was better. She recommended that it was better to buy Mac Air if Mac was my secondary computer. Finally, I made the decision to buy Mac Pro 13 inch because its CPU was better than Mac Air and storage was bigger.
How long to write a book? No correct answer to this question. My sensibility always admire people who can write the book as quickly as possible because the speed implies that they have high productivity and other abilities. My intellects know my sensibility is wrong. How to marry intellects and sensibility? I do not have answer to this question, either. One thing can be confirmed that good books take time. How long? Several years.