How to Customize the Analytics Report?

How to Customize the Analytics Report like Sales Analytics ,Purchase Analytics?
when i try to include field - ‘Sales Person’ as like customer it throws error :

"File "/home/nxweb/frappe-bench/apps/frappe/frappe/desk/report_dump.py", line 22, in get_data
    args = copy.deepcopy(data_map[d])
KeyError: u'Sales Person' "

Can anyone guide me some steps to include a sales person in Sales Analytics Report??

Thanks,
Saranya