Error using symsum and arrays for summing over array elements

Hi all, I have a problem with using symsum and arrays. For example consider the following code, and I get the error 'Error using syms, using input and output arguments simultaneously is not supported '. How could I fix it?

array(1)=0.4;
array(2)=0.99;
array(3)=0.87;
array(4)=0.33;
array(5)=0.33;
array(6)=0.33;
array(7)=0.21;
array(8)=1.3;
array(9)=1.2;
array(10)=0.04;

disp(array)

    0.4000    0.9900    0.8700    0.3300    0.3300    0.3300    0.2100    1.3000    1.2000    0.0400

syms q
trial = symsum( array(syms(q))*q^2 , q,2,7)

Error using syms (line 146)
Using input and output arguments simultaneously is not supported.

Answer 1

[VBBV]

trial = symsum( array(double(q)).*q.^2 , q,2,7)

[VBBV]

q is already defined as sym variable. Using syms inside symsum may not be needed. Doc also symsum function

[Tsz Tsun]

    
array(1)=0.4;
array(2)=0.99;
array(3)=0.87;
array(4)=0.33;
array(5)=0.33;
array(6)=0.33;
array(7)=0.21;
array(8)=1.3;
array(9)=1.2;
array(10)=0.04;
disp(array)

    0.4000    0.9900    0.8700    0.3300    0.3300    0.3300    0.2100    1.3000    1.2000    0.0400

% Unfortunately, it is still not working...
syms q
trial = symsum( array(double(q)).*q.^2 , q,2,7)

Error using mupadengine/feval2char
Unable to convert expression containing symbolic variables into double array. Apply 'subs' function first to substitute values for variables.

Error in sym/double (line 755)
Xstr = feval2char(symengine, "symobj::double", S);

[Torsten]

Symbolic variables can never be used to index an array.

When you have a finite set of things to index in an expression, you should not use symsum() or symprod(): instead you should create the full list of values as arrays, and sum() or prod() as appropriate.

[VBBV]

@Tsz Tsun Just index the range of array elements in the vector as its given in expression and avoid symsum

array(1)=0.4;
array(2)=0.99;
array(3)=0.87;
array(4)=0.33;
array(5)=0.33;
array(6)=0.33;
array(7)=0.21;
array(8)=1.3;
array(9)=1.2;
array(10)=0.04;
disp(array)

    0.4000    0.9900    0.8700    0.3300    0.3300    0.3300    0.2100    1.3000    1.2000    0.0400

trial = sum(array(2:7).*(2:7).^2)

trial = 47.4900

[VBBV]

@Tsz Tsun you could also subs the symbolic variable for that index range and use sum

array(1)=0.4;
array(2)=0.99;
array(3)=0.87;
array(4)=0.33;
array(5)=0.33;
array(6)=0.33;
array(7)=0.21;
array(8)=1.3;
array(9)=1.2;
array(10)=0.04;
disp(array)

    0.4000    0.9900    0.8700    0.3300    0.3300    0.3300    0.2100    1.3000    1.2000    0.0400

syms q
trial = sum(array(2:7).*subs(q.^2, q,2:7))  % subs the variable 

trial = 

double(trial)

ans = 47.4900

[Tsz Tsun]

Thanks a lot, it works well !