# Problem in using symsum

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I am writing a code to solve a problem by least square method. Can someone tell what is wrong in this code?
syms x k
x(1)=-2;
x(2)=-1;
x(3)=0;
x(4)=1;
x(5)=2;
f(1)=-2;
f(2)=-1;
f(3)=0;
f(4)=1;
f(5)=2;
for i=0:4
a(i)=symsum((x(k))^i,k,1,5)
end
Error using sym/subsindex (line 857)
Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be symbolic variables, and function body must be sym expression.
Error in sym/subsref (line 902)
R_tilde = builtin('subsref',L_tilde,Idx);
Error in NMa2q2 (line 13)
a(i)=symsum((x(k))^i,k,1,5)

Edited: Bastian Arturo Romero Mardones on 28 Nov 2020
syms x k
x(1)=-2;
x(2)=-1;
x(3)=0;
x(4)=1;
x(5)=2;
f(1)=-2;
f(2)=-1;
f(3)=0;
f(4)=1;
f(5)=2;
for i=0:4
a{i+1}=symsum((x*(k)).^i,k,1,5) %change this line
end
if you need double variables and not syms, use:
a{i+1}=double(symsum((x*(k)).^i,k,1,5))
did you try using double ()?
a{i+1}=double(symsum((x*(k)).^i,k,1,5))
with double() this is the output maybe i don't understand good your problem, sorry