Mike,
sorry to reply so quickly to my email, but I realized I could have
been clearer. Please replace:
self._data_source["ParticleMassMsun"].sum(dtype='float64')
with
self._data_source.quantities["TotalQuantity"]("ParticleMassMsun")
in both cases.
--
Stephen Skory
s at skory.us
http://stephenskory.com/
510.621.3687 (google voice)