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Yeah that made me twitch also.

In that one case, yeah; I don't think they're going for anything more than general illustration here.

The text that follows does take on a new meaning though, for those that know linear algebra:

If the mere sight of the above is like a punch in the face for you, don't worry.

Almost makes me wonder if it was intentional.

Bears. Beets. Battlestar Galactica!

But what does that illustrate?

Like, what a matrix looks like? Seems fine.

But, as a few people have pointed out, that particular matrix product is undefined. It's broken. That's really not quite what a matrix-vector product looks like.

The author says he has PhD. That's fine. I suffer from the same condition. But it feels off to hear about expertise and see an invalid first example.

Everyone knows you need a 4x4 matrix to do translation, anyway. Now, scale, rotation, and skew...

It also has mixed square brackets and curved parentheses. I stopped reading the article when I saw this.

Brackets can be any shape, it's fine. Like (3)*[4] is still 12. But that matrix-vector product is undefined.