Multiply each column of a matrix by another matrix
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Miguel Morgado
on 9 Apr 2019
Commented: Miguel Morgado
on 10 Apr 2019
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 Comment
Adam
on 9 Apr 2019
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?
Accepted Answer
James Tursa
on 9 Apr 2019
Edited: James Tursa
on 9 Apr 2019
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.
More Answers (1)
Jon
on 9 Apr 2019
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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