Latex equations when uploading a markdown script to wordpress via knit2wp()
You have to load MathJax in your WordPress site. You are recommended to do this through a plugin, or modify your theme if you have write access to it. If you are unable to do either, you may have to manually load it in each single post:
<script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>