depth = [0.0, 1.1, 2.0] * pq.m
depth2 = [0, 1, 1.1, 1.5, 2] * pq.m
s1 = pd.DataFrame({'depth': [x for x in depth]}, index=depth)
s2 = extendAndInterpolate(s1, depth2)
Pandas interpolate data with units