im searching for a solution to recalculate each Value of a persistent item for oh-time-series by factor?
For Example I have 2 Power Items - SolarPower and GridPower. Each Item has the correct Value, but combined for comparison in a Chart it would make sense to invert GridPower *-1.0 so that both lines/areas would be on the same Side. (Like Offset Amount but in this case a factor/multiplication)
Is there a possibility to do that without creating new calculated persistent Items (redundancy)?
A second Y-Axis inverted is nearly what i want but then the auto scaling feature can’t be used.
series:
- component: oh-time-series
config:
name: SolarfixPower
gridIndex: 0
xAxisIndex: 0
yAxisIndex: 0
type: line
item: SolarfixPower
areaStyle:
opacity: 0.2
markPoint:
label:
backgroundColor: auto
data:
- type: min
name: min
- type: max
name: max
- component: oh-time-series
config:
name: GridPower
gridIndex: 0
xAxisIndex: 0
yAxisIndex: 0
type: line
item: GridPower factor??: -1.0
areaStyle:
opacity: 0.2
markPoint:
label:
backgroundColor: auto
Thank you for your Help, i am not sure if i understand you correctly.
It was not my intention to “really” recalculate the Values of the persitent Item in the Database.
I just want to invert the values on the fly for the Chart (without saving additionally). Isn’t this representation layer (=UI)?
If i create a new Item (application layer) updated by rule, then I have to persist the new item (wich would be basically old item * -1) → redundancy.
Yes.
But your question is still about an XY problem. You said you want a solution that does not use additional items for that purpose but that’s a solution, too, and there’s nothing wrong with that.
Now i added a new Item:
Number SolarfixPowerNegative “Solarfix Power negative [%.2f W]” (gBalcony, gPersistence) [“Power”]
and a new Rule:
rule “NegativeSolarPower”
when
Item SolarfixPower changed
then
SolarfixPowerNegative.postUpdate(((SolarfixPower.state as DecimalType).floatValue * -1))
end
→ Using this new Item for the chart is working for me now.
It just hurts a little to have the redundancy in the Database
Now that’s confusing me.
The new created rule for the SolarfixPowerNegative is triggered by changes of the SolarfixPower item
→ the SolarfixPowerNegative Item has now values for the period I created the rule until now.
If I don’t persist this item and use it in a chart, for example for the period of a month, where would the Values come from?
I can see the Chart for the new SolarfixPowerNegative Item starts at the time I created the rule.
That is what I expected - the rule is not computed for the chart - its just computed when the SolarfixPower item changes. So it has no values for the past, and it will lose the calculated values when I not persist them.
A’m I missing something? Is there another way to create a computed Item witch is calculated on the fly?
Ah okay - now it’s clear.
Finally I’ll save both Values in this case. Positive Power is technically the “correct” Value, and negative Power is used for the special Chart.
Hopefully in a future Day there will be a smarter Way to handle this with the new Charts.
For Openhab 2.5 i made a custom Widget with Charting Components from Highcharts that I used in HabPanel.
Recalculating the Values for the charts as other features like synchronous zooming, panning, cursor for multiple Charts are features that I miss in Openhab 3 charts for now.
Overall of course Openhab 3 is in many Ways better and I’m excited to see the next new features…
