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

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Mehdi 2022-9-18

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https://ww2.mathworks.cn/matlabcentral/answers/1807465-how-to-assign-a-symbolic-equation-to-previously-defined-numeric-matrix

编辑： Torsten 2022-9-18

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.

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Mehdi 2022-9-18

在 MATLAB Online 中打开

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   