Need help in coding this summation, please.

Hi,

Can anybody help me with coding this summation into matlab, please:

where J is (3x6), A is (6x6) and Phi is (3x3x9).

I've tried with this code:

 % for ii=1:hor
    for mm=1:ii
        G(:,:,ii)=sum(kron(J*A'^(ii-mm),Phi(:,:,mm)),3);
    end
   end %

but it doesn't seem to work, as I get incorrect results. I think the mistake is in the sum function, but I don't know other way of coding the summation (cumsum function doesn't work either).

I'd really appreciate some help here, as I'm completely stuck.

best,

[Ced]

EDIT: Ignore this rubbish, see next post.

[Luciano Campos]

Hi Ced, Thanks for your comment. I tried what you suggest, but it still won't work. The original formula is correct. If you develop the original summation you get:

I think the problem is that I don't know how to sum up consecutive terms as neither sum nor cumsum function seem to work.

Thanks for your help,

best,

[Ced]

I just found it strange to start G indexing a 1, but Phi indexing at 0.

Yeah, I messed up, sorry. Your original equation looks correct to me, but yes, you sum up too much. With sum, for each mm, you sum up over all of Phi again, which is not what you want.

Assuming you initialize G with zero:

 for ii=1:hor
    for mm=1:ii
        G(:,:,ii) = G(:,:,ii) + kron(J*A'^(ii-mm),Phi(:,:,mm));
    end
 end

Answer 1

[Walter Roberson]

Is the x in a circle indicating cross-product or is it indicating exclusive or?

[Ced]

I believe it stands for the tensor product, hence the kronecker operator.