How to graph the delta (difference) between indoor and outdoor temperature

Grafana InfluxDB
1

  • What Grafana version and what operating system are you using?
    v9.3.6

  • What are you trying to achieve?
    To display the delta between indoor and outdoor temperature

  • How are you trying to achieve it?
    BY filtering on indoor and outdoor temperature and using Transform

  • What happened?
    Don’t know how to do it.

  • What did you expect to happen?

  • Can you copy/paste the configuration(s) that you are having problems with?

from(bucket: “my_bucket”)
|> range(start: v.timeRangeStart, stop: v.timeRangeStop)
|> filter(fn: (r) => r[“entity_id”] == “outside_temperature” or r[“entity_id”] == “indoor_temperature”)
|> filter(fn: (r) => r[“_field”] == “value”)
|> aggregateWindow(every: v.windowPeriod, fn: last, createEmpty: false)
|> yield(name: “last”)

  • Did you receive any errors in the Grafana UI or in related logs? If so, please tell us exactly what they were.
    No errors

  • Did you follow any online instructions? If so, what is the URL?
    I was not able to find instructions.

2

When you send the data to InfluxDB, is the timestamp the same for the indoor temp and outdoor temp?

3

Yes, the timestamp is the same.

4

@snowmangh

Maybe something like this?

from(bucket: "my_bucket")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r["entity_id"] == "outside_temperature" or r["entity_id"] == "indoor_temperature")
  |> filter(fn: (r) => r["_field"] == "value")
  |> aggregateWindow(every: v.windowPeriod, fn: last, createEmpty: false)
  |> pivot(rowKey:["_time"], columnKey: ["entity_id"], valueColumn: "_value")
  |> map(fn: (r) => ({ r with delta: (r.setpoint - r.actual)}))
  |> yield(name: "delta")

I cannot check the above syntax, but it should be close to correct.

5

Thanks for the suggestion. After a re-verification, the timestamp is not quite the same. My bad.

I ended up using the experimental.fill function to draw the delta. Works great, but experimental.

import "experimental"
from(bucket: "my_bucket")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r[“outside_temperature” or r[“entity_id”] == “indoor_temperature”)
  |> filter(fn: (r) => r["_field"] == "value")
  |> aggregateWindow(every: v.windowPeriod, fn: last, createEmpty: false)
  |> experimental.fill (usePrevious:true)