<p dir="auto">The weekly build with nightly wheels from numpy and pandas<br>
has failed. Check the logs for any updates that need to be<br>
made in matplotlib.<br>
<a href="https://github.com/matplotlib/matplotlib/actions/runs/3718330813">https://github.com/matplotlib/matplotlib/actions/runs/3718330813</a></p>
<h3 dir="auto">Bug report</h3>
<p dir="auto"><strong>Bug summary</strong></p>

<p dir="auto">Found this after misunderstanding a question on twitter.</p>
<p dir="auto">Making a plot with a single pixel at a given location is not too tricky, the pixel marker (<code class="notranslate">,</code>) is designed specifically for this purpose, and treated specially by <code class="notranslate">Line2D.draw</code>.</p>
<p dir="auto">However, using scatter instead (where we get a collection object), the "pixel" MarkerStyle is actually many pixels wide.</p>
<p dir="auto"><strong>Code for reproduction</strong></p>

<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import matplotlib.pyplot as plt
fig, ax = plt.subplots()
ax.plot(0, 0, marker=',')  # is actually one pixel
fig, ax = plt.subplots()
ax.plot(0, 0, marker=',')  # is many pixels"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s1">matplotlib</span>.<span class="pl-s1">pyplot</span> <span class="pl-k">as</span> <span class="pl-s1">plt</span>
<span class="pl-s1">fig</span>, <span class="pl-s1">ax</span> <span class="pl-c1">=</span> <span class="pl-s1">plt</span>.<span class="pl-en">subplots</span>()
<span class="pl-s1">ax</span>.<span class="pl-en">plot</span>(<span class="pl-c1">0</span>, <span class="pl-c1">0</span>, <span class="pl-s1">marker</span><span class="pl-c1">=</span><span class="pl-s">','</span>)  <span class="pl-c"># is actually one pixel</span>
<span class="pl-s1">fig</span>, <span class="pl-s1">ax</span> <span class="pl-c1">=</span> <span class="pl-s1">plt</span>.<span class="pl-en">subplots</span>()
<span class="pl-s1">ax</span>.<span class="pl-en">plot</span>(<span class="pl-c1">0</span>, <span class="pl-c1">0</span>, <span class="pl-s1">marker</span><span class="pl-c1">=</span><span class="pl-s">','</span>)  <span class="pl-c"># is many pixels</span></pre></div>
<p dir="auto"><strong>Actual outcome</strong></p>

<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/1475390/81430460-4ae33880-9114-11ea-9323-23b1428c6215.png"><img src="https://user-images.githubusercontent.com/1475390/81430460-4ae33880-9114-11ea-9323-23b1428c6215.png" alt="plot_single_pixel" style="max-width: 100%;"></a><br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/1475390/81430462-4c146580-9114-11ea-845c-bb4356350b78.png"><img src="https://user-images.githubusercontent.com/1475390/81430462-4c146580-9114-11ea-845c-bb4356350b78.png" alt="scatter_single_pixel" style="max-width: 100%;"></a></p>
<p dir="auto"><strong>Expected outcome</strong></p>


<p dir="auto">Both should have markers that are a pixel wide.</p>
<p dir="auto"><strong>Matplotlib version</strong></p>

<ul dir="auto">
<li>Operating system: Debian Jessie</li>
<li>Matplotlib version: master</li>
<li>Matplotlib backend (<code class="notranslate">print(matplotlib.get_backend())</code>): Agg</li>
<li>Python version: 3.7</li>
<li>Jupyter version (if applicable): N/A</li>
<li>Other libraries:</li>
</ul>