Cumulate counts in timechart for sw-rollout

Hi,

I'm looking for a function to cumulate values in a timechart, so I can see a real-time development of a software roll-out - distincted by a UID. The result should look as a ramp.

My search string looks like this:

sourcetype="foo" devicetype="Bob" | timechart dc(uid) as totale by sw | addtotals

This table as an example of the desired results:

Time   # events   w/ new sw    cumulated
Day 1       128         128          128
Day 2       230         102          230
Day 3       220          78          308

So at Day 3 in the example, there are 308 devices with the new software AND it is clear to see, that it doesn't depend primary on how many events where registered.

I think I have to extract the UIDs from one day into a file, to compare them with the UIDs from the next day.

I just tried accum and streamstat, but nothing fits my expectations.

Is there any possibility to solve the problem? This problem is driving me crazy...

Regards ;)