Nodes used when interpolating a node on grid

I have been frustrated by the code below returning NaN---presumably as the first two nodes (`[Inf, 1.0]`) are used to interpolate the queried value (`2`). Is there some way to change which nodes are used when querying a value on the grid?

```julia
using Interpolations
itp = LinearInterpolation([1, 2, 3], [Inf, 1.0, 0.5], extrapolation_bc=Line())
itp(2)
```