Array in a symsum

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Mihai Iustinian
Mihai Iustinian 2021-3-5
评论： Mihai Iustinian 2021-3-6
Hello! I want to implement a formula such F(k)=k*symsum(x(n)*n,n,1,8). There is my code, but i don't know how to put vector x(n) in that sum. It doesn t work.
x=[1 3 5 4]
syms x k n
F(k)=k*symsum(x(n)*n,n,1,4)
That s my code. I want to do>>>>>>>>>>> F(k)=k*[x(1)*1+x(2)*2 +x(3)*3....], but i want the valueof x(1) and x(2)...
So the result may be>>>>>>>>>>>> F(k)=k*[1*1+3*2+5*3+4*4]

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采纳的回答

Walter Roberson
Walter Roberson 2021-3-5
You are attempting to index x with a symbolic variable. That is not possible with MATLAB, and that is something that is not expected to change any time soon.
Construct the definite terms instead
nx = x(:)*(1:length(x));
F(k) = k*nx;
Note that the first line is algebraic matrix multiplication * operator, column * row giving scalar result
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Walter Roberson
Walter Roberson 2021-3-5
Ran in:
syms k
n = 1:128;
Pi = sym(pi);
x = sin(2*Pi*1/32*(n-1));
nx = simplify(n * x(:))
nx = 
F(k) = k*nx
F(k) = 

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