![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1815863/image.png)
- Check whether the “MatrixB” block is configured correctly by validating its expected input dimensions with the output of “u.” Refer to the following documentation to know more about debugging signal dimensions: https://www.mathworks.com/help/simulink/ug/determining-output-signal-dimensions.html
- If the input to “u” is configurable, you can adjust the output to match the dimensions expected by “MatrixB”. This might involve changing the parameterization or gain settings at the upstream block feeding “u”.
- If “MatrixB” needs only one element from the 3-element vector, use a “Selector” block to extract the specific element required.