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

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

Answer 1

[KSSV]

 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.

[S Priya]

Thank you sir.It basically means that...

for i=1:3

C(:,:,1) = [Q11 Q12 Q14;Q12 Q22 Q24;Q14 Q24 Q44]

So, what is the output of

C(:,:,2)=? and C(:,:,3)=?

[Walter Roberson]

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