Accessing previous values from data points to work out flow rate

[dan]

Hey Guys, I'm trying to work out if there is a way to access previous values in a data point's history from the scripting data sources so I can work out flow rate from water level data point in tanks.

I'm thinking I should be able to look at the difference in the values and work out the flow rate in litres per hour or litres per minute, then just update a virtual data point to display it. It's probably so simple I can't see it for looking :O)

I know PREVIOUSVALUE(datapoint) exists as I use it frequently, but is there one for say a minute ago?
Or could I simply mirror a data point value but only update it once a minute, then just work out the flow rate by comparing the current value to the previous only.

Cheers
Dan

[MattFox]

use pt.pointValuesSince(timestamp)
or:

 pointValueAfter(timestamp, cache) 
//function returns the nearest point value/time object after to timestamp, or null if there is not one.

pointValueAt(timestamp, cache) 
//function returns the a point value/time object that was recorded exactly at the timestamp, or null if there is not one.

Fox

[dan]

Thanks mate, I'll give it a go.

[MattFox]

Anytime