How to run this code

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?

Answer 1

[Utkarsh Belwal]

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.

[Ali Najem]

thanks Utkarsh for your reply

yes, thats correct but as you can see in code i cannot use diff becouse elu and inside elu there is two values

i need to obtaine all these equation as a syms

ew12=diff(MSE,w12);
eb12=diff(MSE,b12);
ew34=diff(MSE,w34);
eb34=diff(MSE,b34);

and then pass values to all of them to get answers

note: all these w12 b12 w34 b34 a1 y0 syms are matrix

a1=randn(784,1)*sqrt(2/784);
w12 = randn(300,784)*sqrt(2/784);
b12 = randn(300,1);
w34 = randn(10,300)*sqrt(2/300);
b34 = randn(10,1);
y0=randn(10,1)*sqrt(2/784);

is that possible to get answe i tried many times i stuck with elu function

thanks alot

[Utkarsh Belwal]

I can see that 'elu' function doesn't need symbolic variables so you can do a type conversion before passing it to the 'elu' function as follows:

a2 = elu(double(subs(z2)));
z4 = w34*a2 + b34;
a4 = elu(double(subs(z4)));

[Ali Najem]

thank you so much sir i will try it