MATLAB: Array in a symsum

#sym #symsum #sum #array #vectorMATLAB

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]

Best Answer

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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You should simply check F(k), inside your loop,

 for k = 3:n 
     r = rand(1); 
     if r > terskelverdi
     F(k) = F(k-1) + F(k-2); 
     else
     F(k) = F(k-1) - F(k-2); 
     end
     if F(k)<=0
         F(k) = 0; %if you want to set the last found value to 0
         break
     end
 end

or, after you calculate F, you could set all the negative to 0 (but I don't know if you'd like it this way for your actual problem)

 F(F<=0)=0;

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F = cos(n.*pi.*x).^2;

and the same goes for other cos terms.

Best Answer

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MATLAB: How would i make the for loop stop calculating when it calculates F <= 0? I want the for loop to stop writing. values in F when it hits 0 or less. I have tried "break", but can not seem to get it to work.

MATLAB: Solving a complex integral

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