df <- data.frame(meanValuesHeatingPower = c(1,4,3,7),
meanValuesOutsideTemperature = c(4,3,4,7))
linearModel<-lm(meanValuesHeatingPower ~ meanValuesOutsideTemperature, data = df)
pred<-predict(linearModel, data.frame(meanValuesOutsideTemperature = c(1)))
print(pred)