``` python from pandas import DataFrame import quantities as pq df = DataFrame([[pq.Quantity(i, pq.s)] for i in range(3)]) df[1:] - df[:-1] ``` raises: `ValueError: Unable to convert between units of "dimensionless" and "s"` Note that the following works w/o error because pandas "strips" dimension: ``` python df = DataFrame(pq.Quantity(np.array([0,1,2]).T, pq.s)) df[1:] - df[:-1] ```