ly
works for all widely used retina displays). Set to <code>NULL</code> to
prevent retina scaling. Note that this will always be <code>NULL</code>
when <code>keep_md</code> is specified (this is because
<code>fig_retina</code> relies on outputting HTML directly into the
markdown document).
</p>
</td>
</tr>
<tr class="even" style="vertical-align: top;">
<td>
<code>keep_md</code>
</td>
<td>
<p>
Keep the markdown file generated by knitting.
</p>
</td>
</tr>
<tr class="odd" style="vertical-align: top;">
<td>
<c