title: R plotly: Adjust absolute marker size on 3D scatterplot
body: <p>I am creating a 3D scatterplot using plotly in R and I would like to reduce the marker size of all points.</p>
  
  <pre><code>library(plotly)
  plot_ly(iris,x=~Petal.Width,y=~Sepal.Width,z=~Petal.Length) %&gt;% 
  add_markers(color=~Species)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/VvyjA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VvyjA.png" alt="default"></a></p>
  
  <p>I tried to set the <code>sizes</code> argument, but that doesn't seem to change anything.</p>
  
  <pre><code>plot_ly(iris,x=~Petal.Width,y=~Sepal.Width,z=~Petal.Length) %&gt;%
    add_markers(color=~Species,sizes=0.02)
  </code></pre>
  
  <p>Also tried another argument <code>sizeref</code>. Still, nothing happens.</p>
  
  <pre><code>plot_ly(iris,x=~Petal.Width,y=~Sepal.Width,z=~Petal.Length) %&gt;%
    add_markers(color=~Species,marker=list(sizeref=0.02))
  </code></pre>
  
  <p>Any other solution to decrease the marker size of all points? Or am I doing something wrong?</p>