Symbolic array summation in MATLAB

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Emipel
Emipel 2019-10-7
回答： Jyothis Gireesh 2019-10-10
I am trying to output the following symbolic expression in MATLAB: How can I genereate this?
10*L(1) + 20*L(2) + 30*L(3) + 10*L(4) + 20*L(5) + 30*L(6) + 10*L(7) + 20*L(8) + 30*L(9);
This is my code:
syms J L(k) k
F = J*L(k)
for p = 1:3
P = [10 20 30]';
fff=subs(F,J,P(p))
ss=symsum(fff,k,1,9)
end
The outputted answers are:
10*L(1) + 10*L(2) + 10*L(3) + 10*L(4) + 10*L(5) + 10*L(6) + 10*L(7) + 10*L(8) + 10*L(9)
20*L(1) + 20*L(2) + 20*L(3) + 20*L(4) + 20*L(5) + 20*L(6) + 20*L(7) + 20*L(8) + 20*L(9)
30*L(1) + 30*L(2) + 30*L(3) + 30*L(4) + 30*L(5) + 30*L(6) + 30*L(7) + 30*L(8) + 30*L(9)

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采纳的回答

Jyothis Gireesh
Jyothis Gireesh 2019-10-10
Each iteration of the for loop in the above code creates a new symbolic function "ss" which creates three different expressions. Also, in each iteration of the loop, since the value of “p” is constant, “J” is substituted by the same value.
You may use the following code instead to implement the summation
clear;
syms L(k)
P = repmat([10 20 30],1,3);
ss(k) = sum(P.*subs(L(k),k,1:9));
Hope this helps!!

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