Multiply each column of a matrix by another matrix

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Miguel Morgado
Miguel Morgado 2019-4-9
评论： Miguel Morgado 2019-4-10
Hi,
I have 2 matrices, E of dimension 4x57 and J of dimension 4x4.
I'm trying to do the operation C = sqrt(E'*J*E) for each column of E, so that C ends up being a vector of length 57.
Any ideas of how to do this without a loop?
Thank you very much
  1 个评论
Adam
Adam 2019-4-9
E'*J*E
will result in a 57x57 matrix so what is the operation you are actually trying to achieve in ordder to get a length 57 vector?

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采纳的回答

James Tursa
James Tursa 2019-4-9
编辑：James Tursa 2019-4-9
Another way:
C = sqrt(sum(E.*(J*E)));
For the sizes involved, you probably won't see any significant timing differences between this method and Johathan's method. For much larger sizes, this method does less overall calculations than Jonathan's method and may run faster as a result.

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Jon
Jon 2019-4-9
If I understand your question correctly then the result of the "operation for each column of E" will be on the main diagonal of E'*J*E so you should get what you want using C = sqrt(diag(E'*J*E))

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