Group by part of tag

[pnikos]

Hi,

I have a field and some tags and I am trying to aggregate them per 10s using either stream (preferrable) or batch.
So far it is working fine, but now I need to aggregate using only a part of one of the tags.

E.g. (let's say these happened within the same 10s and I use mean to aggregate):

machine	area	CPU
A01	RF12	12
A02	XF93	08
A03	RF12	16
B01	AF02	14

I want to use only the first digit of the machine, so the result to be:

machine	area	CPU
A	RF12	14
A	XF93	08
B	AF02	14

Any ideas on how this could be done?

Thank you!