I multiply 3x3 and 3x1 matrix and the end result is 3x3 instead of 3x1. What's wrong with the code.?

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Ibrahim Mahmood Shah 2017-3-5

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https://ww2.mathworks.cn/matlabcentral/answers/328244-i-multiply-3x3-and-3x1-matrix-and-the-end-result-is-3x3-instead-of-3x1-what-s-wrong-with-the-code

评论： Ibrahim Mahmood Shah 2017-3-5

k1=[1 -1;-1 1]; x=3 %Number of Elements K=zeros(x+1,x+1); F=zeros(x+1, 1); U=zeros(x, 1); for i=1:x k=k1*AEL(i); F(i+1,1)=F(i+1,1)+(1000*500/x); K(i:i+1, i:i+1)=K(i:i+1, i:i+1)+k; end K2=K(2:x+1, 2:x+1); F2=F(2:x+1, 1); Kinv=inv(K2); U=Kinv.*F2

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Ibrahim Mahmood Shah 2017-3-5

The AEL is as follows [24300000;3.765060240963855e+06;900000]

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Roger Stafford 2017-3-5

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You have used .* instead of *, which is element-by-element, so matlab automatically expands F2 as: repmat(F2,1,3) and then performs the 3 by 3 multiplication element-wise with another 3 by 3 to get a 3 by 3 result. Use just * for matrix multiplication.