Creation of matrix using lower triangular matrix?

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ET-TAOUSSI mehdi
ET-TAOUSSI mehdi 2016-5-10
评论： Guillaume 2016-5-11
Hi everybody. I have a power system that gives me the vector B (containing active P and reactive power Q), and I want to get the vector S (S = A * B) as described in the figure below. Note that the vector B should not be modified. I have already used a lower triangular matrix (in A) but I trouble linking the two powers (P, Q) to obtain the apparent power as is described in the vector S.

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Guillaume
Guillaume 2016-5-10
编辑：Guillaume 2016-5-10
I don't understand what is going in with A but the S as described is:
S = cumsum(hypot(B(1:2:end), B(2:2:end)))
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ET-TAOUSSI mehdi
ET-TAOUSSI mehdi 2016-5-10
The vector B contains other elements that are marked by black points. please the Vector B should not be modified and vector A can contain only null and unit matrices.
Guillaume
Guillaume 2016-5-11
Well, A*B (let's call it T) is the sum of the Pi and Qi. Tn = ∑1...n Pi+Qi, whereas you want Sn = ∑1...n sqrt(Pi^2+Qi^2). You can't express S solely in term of T so what you're asking is not possible.
Now that I understand what A is about, this is how I would do it:
PQ = B(logical(A(end, :)); %Extract P and Q from B
S = cumsum(hypot(PQ(1:2:end), PQ(2:2:end)))
No matter what you do, you will need a way to identify the Ps from the Qs in order to calculate your S. In the above I assume they alternate. If they don't, you'll have to create two different A matrices.

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