title: Can you have a lower or upper triangular matrix plot when plotting correlations using pheatmap in R?
body: <p>Say we use the mtcars data from corrplot. How can we obtain a triangular matrix plot using pheatmap?</p>
  <pre><code>library(corrplot)
  library(pheatmap)
  
  M &lt;- cor(mtcars)
  pheatmap(M)
  
  </code></pre>