Suppose I do a simulation of a model using ModelingToolkit.jl, where `x`

is the state, `y`

is an observed variable, and the solution object is `sol`

. Then

```
sol[x]
sol[y]
```

give vectors of the solution of `x`

and `y`

at the time points given by `sol.t`

(or: `sol[t]`

).

Suppose I instead want an interpolation value?

```
sol(0.5)
```

gives the interpolated value of `x`

at time `t=0.5`

.

- How can I get an interpolated value of
`y`

?