VPIP Standard Deviation

[Se7enUp]

I need to have a statistic that will calculate the Standard Deviation of the VPIP at the gaming table.
I have already calculated the average of the VPIPs at the table with the VPIP stat referring to the table (I selected Table Average in the 'HUD ProfileEditor' in the "Tables Group section").

I looked between the stat and I did not find something to use. So I would like to try to build it but I need a hand to do it.
Given the tools and the knowledge in my possession I can only proceed making an expression that reduces the calculation of the DS in an elementary way

It's correct?
Do you know other ways to do it?

I would then like to develop a statistic to be used in "My Report" that I always calculate the standard deviation of the VPIP but this time, the set of players that are selected by the report filter (in other words those that meet the conditions included in the report).

Can you help me? Here we go.

[WhiteRider]

As far as I'm aware there isn't a simple way to calculate the standard deviation of a stat across multiple players within PT4. You may want to contact one of the custom stat providers (such as ProPokerHuds who have a section in this forum) as they've done some amazing things with the custom stat system, but this is beyond my knowledge I'm afraid.