# How to solve this in matlab?

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Amir Hamzah UTeM on 26 Apr 2011
Hi,did someone know how to convert this equation in matlab?i know this is easy since matlab have build in function.but i cant figure it how to do that in matlab,still new in matlab..
?Xab.Kab
a=1...nth value
b=1...nth value
Xab = X in pattern a and pattern b
Kab = K in pattern a and pattern b
thanks.
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Amir Hamzah UTeM on 26 Apr 2011
i want to solve sum(Xab.Kab) that sum symbol cant view here.. :(
Matt Fig on 26 Apr 2011
So is Walter's solution what you are looking for? If not, and Paulo's is not either, please give a simple example, such as:
X = [2 3 4 8];
K = [7 5 6 9];
What do you want from these two vectors? Or do you need to work on arrays, such as:
X = [2 3; 4 8];
K = [7 5; 6 9];

Paulo Silva on 26 Apr 2011
%pre-allocate the vectors for Xab and Kab
Xab=zeros(1,na+nb-1);
Kab=0*Xab;
% can't decode this %?Xab.Kab
for a=1:na %a=1...nth value
for b=1:nb %b=1...nth value
Xab(a+b-1)=X; %Xab = X in pattern a and pattern b
Kab(a+b-1)=K; %Kab = K in pattern a and pattern b
end
end

Walter Roberson on 26 Apr 2011
I am not at all certain I am interpreting the question correctly, but possibly:
sum(X(:) .* K(:))
Andrei Bobrov on 26 Apr 2011
agree with Walter Roberson,"?Xab.Kab" - as a Maple matrix multiplication rtable - arrays...
Walter Roberson on 27 Apr 2011
sum of a matrix multiplication? Hmmm, possibly. The arrays are an acceptable shape for that.
sum(reshape(X*K,[],1))