title: Removing borders around points in ggplot
body: <p>I have a scatter plot with two different sets of points based on different data sets. I want one of these sets of points to have a border, therefore I have used, <code>pch = 21</code>, which changes the points into circles with a border and an interior.</p>
  <p>I want the other set of points to have no border (for example, removing the red borders in the example below). In the example below, I have still added <code>pch = 21</code> for these points because if I don't use this, then I would have to use colour = Petal.Length, rather than fill = Petal.Length for the colour of the (interior of) the points I do not want to use <code>colour</code> instead of <code>fill</code> because I want the two sets of points to share a legend.</p>
  <p>Is there a way to use <code>pch = 21</code> but then remove the border?</p>
  <pre><code>iris2 &lt;- iris %&gt;% 
    mutate(Sepal.Length = Sepal.Length + 1)
  
  ggplot() +
    geom_point(data = iris,
               aes(x = Sepal.Length,
                   y = Sepal.Width, 
                   fill = Petal.Length),
               pch = 21, colour = &quot;red&quot;, size = 3) +
    geom_point(data = iris2,
             aes(x = Sepal.Length,
                 y = Sepal.Width, 
                 fill = Petal.Length),
             pch = 21, colour = &quot;black&quot;, size = 3)
  </code></pre>
  <p><img src="https://i.stack.imgur.com/zyzpD.png" alt="Plot with red borders" /></p>
  <p>I have tried using <code>stroke</code> to change the border thickness, but while this makes the borders thicker, <code>stroke = 0</code> still gives red borders</p>