Comment on identity theft

neidu3@sh.itjust.works ⁨4⁩ ⁨weeks⁩ ago

• zqwzzle@lemmy.ca ⁨4⁩ ⁨weeks⁩ ago

  A square matrix with the ones in the diagonal is called the identity matrix

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• lugal@lemmy.dbzer0.com ⁨4⁩ ⁨weeks⁩ ago

  It’s an identity matrix. You multiple a vector with it and the result is still the same (identical) vector

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• Gustephan@lemmy.world ⁨4⁩ ⁨weeks⁩ ago

  Eigen see how this is confusing, I don’t get it either

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• pseudo@jlai.lu ⁨4⁩ ⁨weeks⁩ 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: 1 times x is x Identity times anyMatrix is anyMatrix.

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  • fallingcats@discuss.tchncs.de ⁨4⁩ ⁨weeks⁩ ago

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

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    • pseudo@jlai.lu ⁨4⁩ ⁨weeks⁩ ago

      You are right. I will correct it.

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      • fallingcats@discuss.tchncs.de ⁨4⁩ ⁨weeks⁩ ago

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

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    • MBM@lemmings.world ⁨4⁩ ⁨weeks⁩ ago

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

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• Saleh@feddit.org ⁨4⁩ ⁨weeks⁩ ago

  You multiply vectors and matrizes row by column.

  So for any matrix the fitting identity matrix multiplies each row on the relevant position by one and puts it into a column.

  The matrix remains the same.

  See example 5 here: www.geeksforgeeks.org/identity-matrix/

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