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**Step 1:** declaration of symbolic objects using `symmatrix`:
    
    n = 2;

A = symmatrix('A', n);
    lambda = symmatrix('lambda', [n,1]);
    g = symmatrix('g', [n,1]);
    phi = symmatrix('phi', [n,1]);
    l = symmatrix('l', [n,1]);
    item = symmatrix('i', [n,1]);

**Step 2:** declaration of equations:

arga = (l.'*(((lambda).*(A * g)  + (phi.'*lambda) * (A * g))));
    argb = (l.'*(((lambda).*(item) + (phi.'*lambda) * (A * g))));

**Step 3:** differenciating with respect to lambda: `arga` and `argb` should work in the same way, as both `item` and `A*g` are 2x1 vectors. However I cannot run the sum in the parenthesis of the output for `sola` due to dimensionality issues:

sola = diff(arga, lambda)
    solb = diff(argb, lambda)

**Step 4:** Moreover, running the example below, `sola` and `solb` give two different results when substituting `item` with `a*g`, which should not be the case:
    
    l=[1.2;1.1]
    g=[1.9876;1.88]
    phi=[1.0987;1.5192]
    A=[132 123;1222 124]
    item=A * g

Running `sola`, I get the following expression, which I now evaluate with the value of the example:

l.'*((eye(2)) .* A*g + kron(phi.', A*g))

same for `solb`:

l.'*(kron(phi.', A*g) + (eye(2)) .* l)

**ISSUES:**
I was expecting:
1. to be able to execute the sum in the parenthesis in the output of `sola`,
2. to have the same result of sola and `solb` after the evaluation
but that is not the case.

What am I missing?

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Please improve your question. It is not clear what you are asking, the question is badly formatted and the code is spread out across different parts. Please provide a clear, concise minimum example and ask a clear question. As a note: punctuation helps, I had trouble reading your question as it was not always clear where a new sentence started etc.
– pschulz
Commented Apr 4, 2024 at 16:51
"I cannot run the sum in the parenthesis of the output for sola due to dimensionality issues" -- could you please post the full error message you get? I don't have the symbolic toolbox available right now, so cannot run the code to see what you're seeing.
– Cris Luengo
Commented Apr 4, 2024 at 21:52
@CrisLuengo sola = l.'*(symmatrix(eye(2)) .* A*g + kron(phi.', A*g)). Now, symmatrix(eye(2)) .* A*g , is a 2x1 matrix and kron(phi.', A*g) is a 2x2 matrix therefore if i run (symmatrix(eye(2)) .* A*g + kron(phi.', A*g)), I get the following error: "Error using symbolic.mixin.symbolicmatrix/engineHelperWrapper - Dimensions do not match." Which makes sense as I cannot sum a vector and a matrix.
– Simona Ferrero
Commented Apr 5, 2024 at 10:14
@CrisLuengo On the other hand, if I replace A*g which is a 2x1 vector with item which is another 2x1 vector having as elements i, I get l.'*(kron(phi.', A*g) + symmatrix(eye(2)) .* i) where both of the addenda are 2x2 matrices and can therefore be summed.
– Simona Ferrero
Commented Apr 5, 2024 at 10:15
So you found a bug? What do you expect the community here to do? You can report bugs to the MathWorks: supportcases.mathworks.com/mwsupport/s/… — check for existing bug here first: mathworks.com/support/bugreports
– Cris Luengo
Commented Apr 5, 2024 at 13:45

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