Cool article. The first time I've seen linear algebra done in RDBMS was with MadLib, a PostgreSQL extension which implements a lot of these operations https://madlib.apache.org/docs/latest/group__grp__matrix.htm...

So all the operations described in the article, and more are implemented here https://github.com/apache/madlib/tree/master/src/ports/postg...

I'm not sure why Madlib is not mentioned in that CACM article