th joins:
use with right_join() to convert implicit missing values to explicit missing values
use with anti_join() to find out which combinations are missing


nesting() is a helper that only finds combinations already present in the dataset."><meta property="og:image" content="/logo.png"><!-- mathjax --><script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js" integrity="sha256-nvJJv9wWKEm88qvoQl9ekL2J+k/RWIsaSScxxlsrv8k=" crossorigin="anonymous"></script><script src="https://cdnjs.clou