Calculation with items that use Units of Measurement ("%" or "°C")

[Cplant]

I’m running openHAB 3.3 and would like to calculate something (here: the heat index as mentioned here: [SOLVED]How to calculate temperature real feel (feels like, heat index) - #10 by martiniman). I encounter problems during the calculation probably because I calculate with items that use Units of Measurement.

Problem:

• The code runs smoothly, but the heat index calculation is off (e.g. 5450 °C)
• From what I can see, it’s because of the way the temperature and relative humidity is formated on my system / comes in via HomematicIP without any stateDescription / Pattern formating. When I print out those two variables via…
  logWarn("notifications", "Temperature: " + Thermostat_Wohnzimmer_ActualTemperature.state.toString + ", Relative humidity: " + Thermostat_Wohnzimmer_Humidity.state.toString)
  it reads:
  “Temperature: 26.2 °C, Relative humidity: 41 %”
• I believe the wrong calculation occurs because the items use “Units Of Measurement” (the strings “°C” and “%”).

Question: Is there a way to get rid of the strings during the calculation?

[rossko57]

Should help

Working with Number:Temperature Items in rules

openHAB provides Quantity Type features, which can seem baffling. On top of that, Temperature type Quantities have a few quirks all of their own. These notes intend to guide the rules author. I’ve shown work examples in DSL rules language, see below for other scripts examples. All have similar features, if different syntax. Knowing what can be done is half the battle. What is a Quantity Type? Simply, Item states and rule variables may contain Quantities - that just means a number AND a unit …

@Cplant

Is there a way to get rid of the strings during the calculation?

Try not to do that; work with the units.

[Cplant]

Thanks!

@rossko57

openHAB provides Quantity Type features, which can seem baffling.

… is a fair description btw.

This example here…

@rossko57

var numericC = (tempItemC.state as QuantityType<Number>).toBigDecimal

… was the puzzle piece which I was missing.

Got the formula working, so thanks a lot!