title: How can I add specific, labeled points to a ggtern plot?
body: <p>With ggplot2 I normally expect to be able to add a data point like so,</p>
  
  <pre><code>ggtern(df, aes(X, Y, Z, value = VALUE), aes(x, y, z)) +
          geom_point(aes(fill = VALUE), size = 2, stroke = 0, shape = 21) + 
          scale_fill_gradient(low = "red",high = "yellow", guide = F) + 
          scale_color_gradient(low = "red",high = "yellow", guide = F) +
      geom_point(aes(x = 10, y = 10, z = 50), shape = 21)
  </code></pre>
  
  <p>However, when using the ggtern package to generate a ternary diagram they are being inserted into the wrong locations (see example image) with the following warning:</p>
  
  <pre><code>Warning: Ignoring unknown aesthetics: z
  </code></pre>
  
  <p>This implies that ggplot2 is likely attempting to render the point and not ggtern. How can I add specific, labeled points to the ggtern plot?</p>
  
  <p><a href="https://i.stack.imgur.com/X2mbs.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/X2mbs.png" alt="Ternery plot with data point in wrong location"></a></p>