Summation function to calculate Mu

n: n dimension of the equation

D: nxn-dimension Matrix

L: nxn-dimension Matrix

X: n-dimension Vector

S: n-dimension Vector

Hi, I wanted to create a summation function shown in the picture, it seems its hard to implement symsum() function in matlab. So I create a 2 summation function Mu (First summation in the picture) and sumLs (Second summation in the picture). I wanted to ask is there any other way to do this, Is my summation code correct, Sorry I cannot point out the mistake of my function as it involve matrix and vectors calculation. Thanks for any help

To calculate Mu, I call Mu function, In the Mu function, i call sumLs function

function Mu = Muf(n, D, S, X, L)
sumLs = sumLsf(i, L, S);

tempMu = 0;
for i=1:n
    tempMu = tempMu + D(i,i)*(norm(X(i) - S(i) - sumLs))^2;
end
end


function sumLs = sumLsf(i)

global L;
global S;

tempSum = 0;
for j = 1:i-1
    tempSum = tempSum + L(i,j) * S(j); 
end
sumLs = tempSum;
end

[Walter Roberson]

http://www.mathworks.com/help/matlab/math/parameterizing-functions.html

You should avoid using global.

Question: where does the variable Si come from inside Muf, and why do you global S in Muf when you do not use that variable?

[Caleb Goh]

I made a mistake in function Muf i have edit Si to S thanks for pointing out, I edited to pass arguments to the functions instead of accessing global variables

[Alvin Ang]

I am experiencing the same issues too, could someone point out whether the code written above is correct?

Answer 1

[Voss]

The sum over j depends on i, so you must call sumLsf each time through the i loop

function Mu = Muf(n, D, S, X, L)
Mu = 0;
for i = 1:n
    sumLs = sumLsf(i, L, S);
    Mu = Mu + D(i,i)*(norm(X(i) - S(i) - sumLs))^2;
end
end


function sumLs = sumLsf(i, L, S)
sumLs = 0;
for j = 1:i-1
    sumLs = sumLs + L(i,j) * S(j); 
end
end

[Caleb Goh]

Thank you for correcting my mistake, but I implement on my sphere decoder it didn't work as expected maybe its my other code gave that error. I'll try to solve it