Using pybamm's Integral class

[isaacbasil]

Hi, I think I must have misunderstood the use of pybamm's Integral operator, as I am not getting the results I'd expect. For example, to solve,
$\int_{0}^{R}{f(r)}dr$
I am writing,
pybamm.Integral(f(r), r)
Where r is a SpatialVariable, for example,
r = pybamm.SpatialVariable("r", domain=["positive particle"], coord_sys="cylindrical polar")
and I define the geometry as,
"positive particle": {r: {"min": pybamm.Scalar(0), "max": R}
However, even with the simplest possible integral,
$\int_{0}^{R}{1}dr$
I am not getting the value I would expect (the radius of the positive particle). In other words,
$\int_{0}^{R}{1}dr\neq R$
What am I doing wrong here?