and <code>.iteration</code> columns) indexing draws. It should be a grouped by any
columns that are not intended to be nested.</p></li>
<li><p>For <code>unnest_rvars()</code>, the data frame should have at least one column that
is an <code><a href="https://mc-stan.org/posterior/reference/rvar.html" class="external-link">rvar</a></code>; all <code>rvar</code> columns will be unnested.</p></li>
</ul></dd>

</dl></div>
    <div id="value">
    <h2>Value</h2>
    <p>For <code>nest_rvars()</code>, returns a data