Horizontal grid lines in plotly R
<p>The standard R plotly scatter/line graph comes with both vertical and horizontal grid lines. I cannot find the command to select only vertical or horizontal lines. I want the latter. So far I have found the following commands in the <a href="https://plot.ly/r/axes/" rel="noreferrer">offiial guide</a>:</p>

<pre><code>showgrid = FALSE/TRUE
gridcolor = ...
gridwidth = ...
</code></pre>

<p>Any idea which is the command to select subset of grid lines?</p>