How do I create a rule that compares values of two items

Setup, Configuration and Use Beginners
1

I am new to Openhab and have two number items to measure temperature from two different locations. I want to create a rule to compare the value of the two sensors and the create an action if there is a difference of say 5 degrees.

2

Hi,

not exactly what you need - but I hope it helps you to create our own rule. This is one of my rules I use to control the temperature (soll: target, ist: actual):

rule "HeizungEingang"
  when
    Time cron "0 0/30 * * * ?" 
    or Item heizungEingangTargetTemperatur changed
  then
    zWaveValve48Mode.sendCommand(0x1F)
    var double soll = (heizungEingangTargetTemperatur.state as DecimalType).doubleValue
    var double ist  = (zWaveSensor25Temperature.state as DecimalType).doubleValue
    
    if ((mqttPresencePatrik.state == OFF) 
     && (mqttPresenceKarin.state  == OFF)) {
     	soll = soll - 1.5
    }
    
    if ((ist + 2) < soll)         { heizungEingangEG.sendCommand(100) } 
     else if ((ist + 1) < soll)   { heizungEingangEG.sendCommand( 75) }
     else if ((ist + 0.5) < soll) { heizungEingangEG.sendCommand( 50) }
     else if (ist == soll)        { heizungEingangEG.sendCommand( 25) }
     else { heizungEingangEG.sendCommand(0) }
  end
3

Thanks Patrik, that works for me