# What does C(:,:,i)=[Q11 Q12 Q14;Q12 Q22 Q24;Q14 Q24 Q44]; signify?

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S Priya on 1 Sep 2021
Commented: Walter Roberson on 1 Sep 2021
What does C(:,:,i)=[Q11 Q12 Q14;Q12 Q22 Q24;Q14 Q24 Q44]; signify?

KSSV on 1 Sep 2021
C(:,:,i)=[Q11 Q12 Q14;Q12 Q22 Q24;Q14 Q24 Q44];
In the above C, is 3D matrix initialized as 3*3*p matrix. Each matrix of C, should have a 3x3 matrix. The line says there is a loop (i is the index shown here), for the i'th idex in C, a 3x3 matrix is filled in C. The matrix in RHS is a 3X3 matrix and it's each value is denoted by Q11....Q44, where these values should be either calculated or initilaized.
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Walter Roberson on 1 Sep 2021
If you only assign to C(:,:,1) inside the for loop, then after the for loop:
• if C did not exist before the for loop, then C(:,:,2) does not exist
• if C did exist before the for loop, but its size in the third dimension and all following dimensions was 1 before, then C(:,:,2) does not exist
• if C did exist before the for loop, and at least one dimension from the third onward was 2 or more, then effectively C gets resized like reshape(C,size(C,1), size(C,2), []) and then (:,:,2) of the result would be extracted