For user specified functions, the parser in R-studio returns an error when attempting to return a M x N vector (base-type mismatch). e.g.:

```
vector function_A (vector input_A, vector input_B){ // input_A and input_B are 4x1 vectors
vector[4] output[2]; // two 4x1 vectors
output[1] = input_A;
output[2] = input_B;
return output;
}
```

Should I just use a MxN matrix type then?

[EDIT] forgot to ask, “why is that?”

Thank you for your time,

Chiot