If I’m going to occasionally write posts about math (and that is the plan), I need the ability to render equations. It’s not a strict necessity; you can get pretty far by literally describing what it is that you’re trying to say. For example:

The Riemannian gradient over the compact Stiefel manifold of the Rayleigh quotient with respect to some square matrix and a given conformal subspace can be computed as the orthogonal complement with respect to a basis for that subspace of the product of said matrix and said basis.

However, though it may not be worth a thousand words, an equation in this case is worth approximately fifty words:

<div>\$\$\nabla\ \textrm{RQ}_A(\textrm{colspan}(V)) = (I - VV^T)AV\$\$</div>
Or, appropriately rendered:
$$\nabla\ \textrm{RQ}_A(\textrm{colspan}(V)) = (I - VV^T)AV$$

Fortunately, there are more solutions for this than the last time I looked (approximately ten years ago). And if you Google “math, latex and hugo” (as I did), you find the following on the official Hugo website: MathJax support in Hugo.

And so, because I’m a fan of test-driven development, I wrote up this post with a little math (i.e., the block math above) and this inline SVD here: $A v_i = u_i \sigma_i$. And because I hadn’t gone through the steps in the post above, it looked like shit (i.e., the test failed):

This post before MathJax support

But when you add in the steps from the article to add MathJax support to all pages (e.g., in the footer), it’s mostly good. My text editor (vim) still doesn’t understand the LaTeX subscript underscores in the markdown files:

Vim thinks this is bad markdown

But I can deal with that in a few ways: ignore it, or tell vim not to do syntax highlighting on markdown files (set filetype). I’ll update this post if I find a better solution. But in the meantime, I don’t have any excuse not to do math posts.

Update: MathJax pops up obnoxious loading/processing messages in the browser while it is loading. You can disable this by setting messageStyle to 'none', like so:

<script type="text/x-mathjax-config">
MathJax.Hub.Config({
  messageStyle: 'none',
  showProcessingMessages: false,
  tex2jax: {
    // tex2jax config...
  }
});
</script>