Installing rstan...

1. Go to https://mc-stan.org/users/interfaces/rstan
   (can find by googling "rstan")

2. Click on the "RStan Quick Start Guide" under "Download and Get
   Started"

   (Note: We will be installing Stan to run in R.  There are also
   installations for python, matlab, julia, stata, mathematica, scala,
   etc..  If you are interested, see https://mc-stan.org/ for details.)

3. Follow the instructions for configuring the C++ Toolchain on your
   computer

   * This is the trickiest part of installing Stan in R on your
     computer.

   * There are separate instructions for Windows, Mac, & Linux

   * Make sure you are using R version 4.0 or higher.  You may want to
     update Rstudio to the current version as well (you need at least
     version 1.2.5042).

   * MAKE SURE YOU ARE following the instructions for your version of
     R (version 4.0 or higher) not an earlier version of R such as
     version 3.6, etc.  
     
4. Follow the instructions under "Installation of RStan" and "Verify
   Installation"

   * The most important parts are the "install.packages" command, to
     actually do the installation, and the "example" command to verify
     that your installation is good.  If you can get these two
     commands to run successfully, you are golden.

     -- Note: the "example" command will take from several seconds to
        up to a minute or so to run.  It will also generate a ton of
        output that may not make much sense right now... Be patient...

   *  Please note the other instructions under these two headings,
      which handle some common special cases that you may need to deal
      with on your laptop.

5. After you have verified that your installation is good, feel free
   to browse through the longer "How to Use RStan" section.  As you
   get more accustomed to Stan, you'll see that the Stan modeling
   language is a kind of extension of R's usual programming language
   -- much more general and flexibe than lmer()'s modeling language.

6. Check out https://mc-stan.org/ for background info on stan.