Why does Simulink Product block (element-wise .*) fail for [3x5] .* [1x5] while MATLAB Function block works?

I have a Simulink model with two signals:

• U = repmat(2,3,5) → size [3x5]
• x = [1 2 3 4 5] → size [1x5]

In a MATLAB Function block, this works, but with a Product block set to element-wise multiplication, I get dimension errors like:

I expected the Product block and MATLAB Function block to behave the same.

Does the Product block support implicit expansion/broadcasting for singleton dimensions (like [1x5] to [3x5])? If not, what is the recommended Simulink-native way to do this without a MATLAB Function block?

Answer 1

[Fangjun Jiang]

You are correct. Simulink does not support implicit expansion. For alternatives, see this Q&A.

https://www.mathworks.com/matlabcentral/answers/2182670-subtracting-a-vector-from-a-variable-sized-matrix-in-simulink-issue