MATLAB: How to run this code

differential equationsmatlab functionsolve

please can anyone know how to run this code

syms w12 b12 w34 b34 a1 y0  
z2 = w12*a1 + b12;
a2 = elu(z2);
z4 = w34*a2 + b34;
a4 = elu(z4);
MSE=1/2*(a4-y0).^2; 
ew12=diff(MSE,w12);
eb12=diff(MSE,b12);
ew34=diff(MSE,w34);
eb34=diff(MSE,b34);

and the elu is a function which is

function fr = elu(x)
    f = zeros(length(x),1);
    for i = 1:length(x)
    
        if x(i)>=0
        f(i) = x(i);
    else
        f(i) = 0.2*(exp(x(i))-1);
        end
        
    end
    fr = f;
end

any suggestions?

Best Answer

Hello Ali,

I can see that you have declared symbolic variables and then you are passing these variables to the ‘elu’ function. In the function you are comparing a symbolic variable with a numerical value which is not possible and that’s why you are getting an error.

To do a comparison you have to substitute the symbolic variable with a value and for that you can use the Symbolic Substitution in MATLAB. Please refer to the documentation for more information.