Avoid for loops, use cell operation to do: r2' * r1 * l1' * l2

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Xh Du 2017-5-9

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https://ww2.mathworks.cn/matlabcentral/answers/339436-avoid-for-loops-use-cell-operation-to-do-r2-r1-l1-l2

评论： Stephen23 2017-5-9

Hi all,

Say I have 2 simple 1-by-2 cells, I'd like to perform operation like this: r2' * r1 * l1' * l2 to obtain a 2-by-2 matrix, sample code as follows:

clear; clc;
% the cells.
bl = {1 2};
br = {3 4};
% element 1.
l1 = bl{1, 1};
l2 = bl{1, 1};
r1 = br{1, 1};
r2 = br{1, 1};
otpt11 = r2' * r1 * l1' * l2;
% element 2.
l1 = bl{1, 2};
l2 = bl{1, 1};
r1 = br{1, 2};
r2 = br{1, 1};
otpt12 = r2' * r1 * l1' * l2;
% element 3.
l1 = bl{1, 1};
l2 = bl{1, 2};
r1 = br{1, 1};
r2 = br{1, 2};
otpt21 = r2' * r1 * l1' * l2;
% element 4.
l1 = bl{1, 2};
l2 = bl{1, 2};
r1 = br{1, 2};
r2 = br{1, 2};
otpt22 = r2' * r1 * l1' * l2;
% put all elements together.
otpt = [otpt11 otpt12; otpt21 otpt22];

I can probably use for loops to do it, but I'd like to use a compact operation such as cellfun to do it, which I believe is faster and more nature for cells.

Many thanks!