MATLAB: Most efficient way of creating variables

Question

I have 8 matrices, (13×10) ,which contain velocites of a flow within a channel (V1,V2…..V8). For each of these I have extarcted the lasts columns using the following :

E1 = V1(:,10);

E2 = V2(:,10);

E3 = V3(:,10);

……

E8 = V8(:,10);

I read the following https://uk.mathworks.com/matlabcentral/answers/57445-faq-how-can-i-create-variables-a1-a2-a10-in-a-loop which mentions that dynamic variable names should be avoided where possible.

In accordance, I attempted to try what the post suggested (Making one matrix with the 8 columns (E):

E = zeros(13,8); % Each column to be replaced by the last columns of V1,V2..V8

for i = [1:8];

E(i) = V(i)(:,10); % Trying to assign final columns of V1,V2..V8 to the columns of E8

end

However, I feel as if this is very far from the correct way of doing this. Any help is appreciated

Answer 1

It's good that you're following that advice.

E = [V1(:,10), V2(:,10), . . ., Vn(:,10)]; % most efficient method of this list

If you want to use a loop, the variables have be to combined before hand,

V = {V1, V2, V3, . . ., Vn};
E = zeros(size(V1,1), numel(v)); 
for i = 1:numel(V)
    E(:,i) = V{i}(:,10); 
end

or, if the Vn matrices are all the same size,

V = cat(3, V1, V2, V3, . . ., Vn);
E = squeeze(V(:,10,:));