title: Mapping of shapes in ggplot
body: <p>I have the following sample code:</p>
  <pre class="lang-r prettyprint-override"><code>df &lt;- data.frame(name = c(&quot;a&quot;, &quot;b&quot;, &quot;c&quot;),
                   date = as.Date(c(&quot;2020-01-01&quot;, &quot;2020-01-03&quot;, &quot;2020-01-05&quot;)),
                   pch = c(18, 19, 1))
  
  ggplot(data = df, aes(x = date, y = name)) + 
    geom_point(aes(shape = pch)) 
  </code></pre>
  <p>I would like to use the shapes 18, 19 and 1 (just as specified in the column <code>pch</code> of my data). Unfortunately, when I have numeric values in the column <code>pch</code> I get the message &quot;A continuous variable can not be mapped to shape&quot;, but when I convert them into a factor I dont get the shapes I want because ggplot assigns the shapes automatically to my factor levels. What can I do?</p>