I have described in depth how a classic thermostat models the house so as to have requisite variety. Now I wonder how my digital setback thermostat decides when to turn the heat on each morning.
A mercury switch activates a solenoid in the furnace. But the control is analog, not binary, where ambient temperature modulates a pulse duty cycle.
We have digital records and have charted by hand before.
Outside Temp vs. Furnace Restart Time
Now we consider how we might automate the extraction and collection of these measurements through automation.
Inside temp cycles as the outside temp falls.
Note: the sample graph above models the data but does not model the thermostat. To complete the investigation we would need to build a model that with only observed temperature can duplicate with some fidelity the start time variation. See Iris van Rooij nature 
Daily Highs and Lows records new events.
http://data.ward.dojo.fed.wiki/assets/page/how-data-works/accumulated-high-low.html HEIGHT 300
This item holds the recorded data within its page json and invokes the html script that formats it. github
http://data.ward.dojo.fed.wiki/assets/page/how-data-works/plot-intervals.html HEIGHT 400