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identity theft (lemmy.dbzer0.com)
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[-] pseudo@jlai.lu 12 points 15 hours ago* (last edited 14 hours ago)

That matrix of zeros with one in diagonal is called the matrix of identity.
It is famous because when doing multiplication on matrix or vector, it acts likes 1 on "normal" number:
x times 1 is x anyMatrix times Identity is anyMatrix.

[-] fallingcats@discuss.tchncs.de 4 points 15 hours ago

Wouldn't you need to put anyMatrix first, since matrix multiplication isn't commutative?

[-] pseudo@jlai.lu 2 points 14 hours ago

You are right. I will correct it.

[-] fallingcats@discuss.tchncs.de 1 points 14 hours ago* (last edited 7 hours ago)

No I just tried it and I was wrong, it seems like it doesn't matter for the ID matrix specifically

[-] pseudo@jlai.lu 1 points 10 hours ago

I need to freshen up on my linear algebra. I don't remember on which sense it goes but I think if you swap the factors, you'll have to you transpose the matrix x to keep the same result.

[-] MBM@lemmings.world 1 points 14 hours ago

Huh? Identity times anyMatrix is also anyMatrix. The matrix just has to have the right dimensions

this post was submitted on 15 Mar 2025
523 points (98.3% liked)

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