[UrbanSim-Users] sum_dataset_over_ids()

Hello,

I try to use the function "sum_dataset_over_ids()", for example to compute
the number of households in each gridcell or number of jobs.

When I used it to run UrbanSim I received the following message.

"StandardError: Unknown function sum or error occured during evaluation."

I attached the complete log of households and jobs computing.

Can someone please help me to correct this error?

Thanks a lot.

Hakim.
Paris.