types</code></td>
<td align="left">Optional name of the output column of matrix column
types</td>
</tr>
<tr class="odd">
<td align="right"><code>drop</code></td>
<td align="left">Optional value to be dropped from output (often 0)</td>
</tr>
</tbody>
</table>
<p>Prior to <code>expand</code>ing, it is usually necessary to
<code>gather</code> columns of matrices.</p>
<div class="sourceCode" id="cb7"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">etas_forgraphing</span> <sp