compare with previous attribute

I would like to compare an attribute (or computed attribute) with the previous value and I dont know if it is possible.
I am getting from time to time a small increase in fuel from the device which corrects itself and dont want to see those fluctuations in the graph.

Would processing.computedAttributes.lastAttributes help in this case ? And if so, what would be the configuration and how to use the previous value in the computed attributes expression ?

Yes, you can enable processing.computedAttributes.lastAttributes. You need to prefix attributes with last. For example, fuelLast.

did not understood if it is with capital L or not as you wrote both ways :) But will try with capital:

Attribute: Fuel
io48 ? (io48 - io48Last) == 1 ? io48Last * 0.7 : io48 * 0.70 : null

io48 fuel percentage, if it increases by 1% then keep the previous value in fuel (0.7 - 70 litres fuel tank). Hope the expression is correct.

Sorry, it's actually a prefix. It should be lastFuel.

I added the configuration:

<entry key='processing.computedAttributes.lastAttributes'>true</entry>

but the following still gives undefined lastio48 on the test message

io48 ? (io48 - lastio48) == 1 ? lastio48 * 0.7 : io48 * 0.70 : null 

ignore the undefined on the test message or is there an issue with lastio48 that I am missing ?

It should be lastIo48.

It worked perfectly. Thanks Anton. So after the prefix, the attribute must be with capital first letter.

Correct.

I realized that comparing with the previous io48 will not work if there will be 2 consecutive io48 with wrong values (slightly increased).

I tried using lastFuel but apparently it is not working :

Attribute: Fuel ```
``` Expr: (lastFuel && io48) ? ((io48- lastFuel) > 0 && (io48 - lastFuel) < 3 ) ? lastFuel : io48 * 0.70 : null ```

Does it not work to take previous computed attribute and only works to take previous attributes reported by the device ?

Previous computed attribute should work.