how to vectorize squared function

Question

Maximilian Dio 2021-7-22

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https://ww2.mathworks.cn/matlabcentral/answers/883644-how-to-vectorize-squared-function

编辑： Bruno Luong 2021-7-22

在 MATLAB Online 中打开

Hi I have a problem considering calculating a squared function of a grid

so I have 2 vectors X=rand(N,D) and Y=rand(M,D)

I want to generate a function that returs a matrix s.t.

for i = 1:N
            for j = 1:M
                r2(i,j) = (X(i,:)-Y(j,:))*L*(X(i,:)-Y(j,:))';
            end
        end

is there a way to vectorize this cleverly?

It needs to run in Simulink (code generation)

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Answer 1

KSSV 2021-7-22

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https://ww2.mathworks.cn/matlabcentral/answers/883644-how-to-vectorize-squared-function#answer_751644

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r2 = (X-Y).*L.*(X-Y)';

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Answer 2

Bruno Luong 2021-7-22

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https://ww2.mathworks.cn/matlabcentral/answers/883644-how-to-vectorize-squared-function#answer_751649

编辑：Bruno Luong 2021-7-22

在 MATLAB Online 中打开

X=rand(3,10);
Y=rand(4,10);
L=rand(10);
N=size(X,1);
M=size(Y,1);
XX=reshape(X,N,1,[]);
YY=reshape(Y,1,M,[]);
YX=reshape(XX-YY,N*M,[]);
r2=reshape(sum(YX.'.*(L*YX')),[N M])
r2 = 3×4
   -0.0902    0.5037    1.1533    1.2152
    0.2232    0.4179    1.9723    1.8407
    0.4105   -0.1182    2.4237    3.2231