Fira Code in RStudio! For U-Linux!
(version 1.2.5001 on Ubuntu 18.04 LTS 64bit)
Just my past quick notes. YMMV...
Hope this helps you.
Go Huskies! 
QUICK WAY:
- In Rstudio Terminal: $ sudo apt install fonts-firacode
- Restart Rstudio
- in Tools / Appearance / Editor Font: choose FIRA Code and Apply.
- Enjoy! Test in Console Panel: x <- abc (for arrow shortcut: ALT-minus).
(arrow will now appear as smooth Ligature arrow!)
note: fira fonts files should be in home/share/usr/fonts
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First: D/L the FiraCode Font:
Rstudio INSTR... DL&Install: go here 1st!
RStudio instructions · tonsky/FiraCode Wiki · GitHub
GIT:
GitHub - tonsky/FiraCode: Free monospaced font with programming ligatures
direct D/L link: might not be the latest version - CHECK!
https://github.com/tonsky/FiraCode/releases/download/1.205/FiraCode_1.205.zip
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Second: In the root/usr/share/opentype/firacode folder:
double-click each TTF font file
and click “Install font”;
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Here's how you get there:
(to INSTALL DL Fonts) in Rstudio:
(1) Download and install @FiraCode,
(2) in @rstudio, go to Tools > Global Options > Appearance,
(3) change font to Fira Code,
(4) TICK "Use ligatures", and
(5) marvel at the beautiful code! @rstudiotips YES!