t be used before conditioning in the formula.
If you have need of logical or, we suggest creating a new variable that contains the
results of evaluating the expression.</p>
<p>Similarly, addition (<code>+</code>) is used to separate grouping variables, not for
arithmetic.</p>
    </div>

    <div id="ref-examples">
    <h2>Examples</h2>
    <div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span><span class="fu">df_stats</span><span class="op">(</span> <span class="op">~</span> <spa