I want to save all .R file in one type of encoding, it is inconvenient to switch encodings everytimes I open a file, so, how to change the character encoding of .R file in RStudio?

R 3.4.3; RStudio 1.1.383 Tools > Global Options > Code > Saving > "Default text encoding" [Change] <img src="https://i.stack.imgur.com/cKiOd.png" alt="enter image description here">

<code>Tools</code> - <code>Options</code> - <code>General</code> - <code>Default text encoding:</code> <img src="https://i.stack.imgur.com/NGRem.png" alt="enter image description here">