Convert a Time-Indexed Vector to Function of Time (i.e. x = f(t))

This is just added code to vec_fun()- need to think about better separation of responsiblities

interpolate_vec(x, t = vec_seq_along(x))

Arguments

x

A vector to interpolate

t

An optional time index; if empty, interpolate_vec() will use the index of x

Value

A (thrice) differentiable function interpolating t and x