</p>
<ul>
<li>unless the variable is called in <code>x</code>, it will be added to
the formula in the first position after the optional <code>alpha</code>
variable.</li>
</ul>
</li>
<li>
<p><code>conds</code> : select a variable to condition on</p>
<ul>
<li>declared as <code>conds = product(cond1, cond2, ...)</code>
</li>
</ul>
</li>
</ul>
<p>These values are then sent through repurposed
<code>productplots</code> functions to create the desired formula:
<code>weight ~ alpha + fill + x | conds</code>. Becaus