rscore (<code>_</code>) symbol, but nothing else (and a variable name cannot begin with a number). BUGS variables can also include the dot, or period (<code>.</code>) symbol.</p>
<p>In Stan, the second argument to the “normal” function is the standard deviation (i.e., the scale), not the variance (as in <em>Bayesian Data Analysis</em>) and not the inverse-variance (i.e., precision) (as in BUGS). Thus a normal with mean 1 and standard deviation 2 is <code>normal(1,2)</code>, not <code>normal(1,4)</code> 