title: Error: A continuous variable can not be mapped to shape
body: <pre><code>ggplot(penguins)+
     geom_point(mapping=aes(x=flipper_length_mm,y=body_mass_g,shape=year))
  </code></pre>
  <p>this is the code using <code>palmerpenguins</code> dataset and why it is not working?
  can someone help me out</p>
  <blockquote>
  <p>Error: A continuous variable can not be mapped to shape</p>
  </blockquote>