Build determinantes of matrices in cell arrays

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Ahmed Hossam 2017-4-19

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https://ww2.mathworks.cn/matlabcentral/answers/336089-build-determinantes-of-matrices-in-cell-arrays

评论： Jan 2017-4-19

I have a cell array X with dimension (N x 2) and N is an even number. This cell array is filled with (2 x 2) Matrices of type double.

I'm wondering, if there is a way to build the determinants of each of those matrices (type: double) in a vectorized manner without using a for loop.

My solution was:

   Y = zeros(N,1)
for i = 1:N
   Y = det(X{i});
end

Now I have this Y of size (N x 1), which will contain all the determinants of the (2 x 2) matrices stored in the cell array X with size (N x 2).

Can I "vectorize" the for loop in some way or the other?

Thanks for having a look at this!

采纳的回答

KSSV 2017-4-19

1
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https://ww2.mathworks.cn/matlabcentral/answers/336089-build-determinantes-of-matrices-in-cell-arrays#answer_263580

在 MATLAB Online 中打开

doc cellfun

N = 4 ;
X = cell(N,2) ;
for i = 1:N
    X{i,1} = rand(2) ;
    X{i,2} = rand(2) ;
end
detX = cellfun(@det,X) ;

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Stephen23 2017-4-19

编辑：Stephen23 2017-4-19

@Ahmed Hossam: it is seldom required to calculate a matrix inverse. If you are solving systems of equations, then MATLAB has much better methods available. Read the inv help carefully to know what the "more effective" methods are.

Jan 2017-4-19

While the cellfun method is nice, it is not "vectorized" actually. You only do not see the loop anymore. Internally you cannot treat the cell elements in a vectorized way.

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