How to assign a symbolic equation to previously defined numeric matrix?

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I have a vector that at the first stage it contains numeric values, but later must be assigned by symbolic equations. How is it possible in Matlab?
As a short example:
clear
syms eta__2 zeta__2
Wxy2(1)=1;
Wxy2(1) = legendreP(1, zeta__2)*legendreP(1, eta__2) ;
Unable to perform assignment because value of type 'sym' is not convertible to 'double'.

Caused by:
Error using symengine
Unable to convert expression containing symbolic variables into double array. Apply 'subs' function first to substitute values for variables.
  5 Comments
Mehdi
Mehdi on 18 Sep 2022
clear
syms eta__2 zeta__2
sym('Wxy2')=[0, 0, 0];
Unable to perform assignment because the indices on the left side are not compatible with the size of the right side.
for r=1:3
for i=1:11
for j=1:11
Wxy2(r) =legendreP(i, zeta__2)*legendreP(j, eta__2) + Wxy2(r);
end
end
end
Torsten
Torsten on 18 Sep 2022
Edited: Torsten on 18 Sep 2022
syms eta__2 zeta__2
Wxy2 = sym('Wxy2',[1 3]);
Wxy2(1:3) = sym('0');
for r=1:3
for i=1:11
for j=1:11
Wxy2(r) =legendreP(i, zeta__2)*legendreP(j, eta__2) + Wxy2(r);
end
end
end
Wxy2
Wxy2 = 

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