4, &quot;,&quot;)
}

do_comma &lt;- function(x){
  if (is.list(x))
    lapply(x, paste, collapse=&quot;, &quot;)
  else
    paste0(x, collapse=&quot;, &quot;)
}
</code></pre>

<h2>Michaelis menten</h2>

<pre><code class="r">N &lt;- 3
y &lt;- as_sym(matrix(paste0(&quot;y&quot;, 1:N)))
x &lt;- as_sym(matrix(paste0(&quot;x&quot;, 1:N)))
b &lt;- as_sym(paste0(&quot;b&quot;, 1:2))

num &lt;- b[1] * x
den &lt;- b[2] + x
</code></pre>

<h2>Different representations</h2>

<pre><code class="r">## mu a matrix; a conv