I’m currently using `ode_bdf_tol`

, which returns an array of `T`

vectors, each of size `N`

, where `T`

is the number of timepoints and `N`

the number of state variables. My data is a sum of a subset of the states, so I would like to do something like the following:

```
data {
real x[T];
}
transformed_data {
vector[N] w = [0, 0, 0, 1, 1, ..., 1]'; // select states to sum
}
model {
vector[N] sol[T];
sol[1:T] = ode_bdf_tol(...); // an array of vectors
to_matrix(sol[1:T]) * w // I want to do something like this
}
```

Conceptually, I’d like to ‘stack’ the array of vectors from `ode_bdf_tol`

's output into a `T x N`

matrix, which would enable the above and other vector/matrix operations. Is this something that’s currently supported?

Thanks!