Showing a current value

Grafana Dashboards
1
  • What Grafana version and what operating system are you using?

Grafana 9.2.2 on Fedora 35

  • What are you trying to achieve?

In a graph I display the setting of a thermostat.

  • How are you trying to achieve it?

I use Graph types > Line interpolation > Step after.

  • What happened?

The thermostat setting is only displayed when the value changes. E.g. if the setting is 15 and goes to 20 at 08:00, the graph has a vertical line from 15 to 20 at 08:00.

  • What did you expect to happen?

What I would like to happen is a way to obtain a horizontal line at 20 from 08:00 to the current time. The actual setting at e.g. 10:00 is still 20 and will remain 20 until the next value change.

Is this possible?

2

What is your datasource and can you share the query you have written thus far?

3

Datasource is a PostgreSQL database.

The query I currently use is

SELECT
  $__time(last_updated),
  state ::decimal as "heating temp"
FROM states
WHERE
  $__timeFilter(last_updated)
  AND entity_id = 'number.boiler_heating_temperature'
  AND state ~ '^[-0-9.]+$'
ORDER BY 1

I know I can artificially add a final value, e.g.

SELECT
  $__time(last_updated),
  state ::decimal as "heating temp"
FROM states
WHERE
  $__timeFilter(last_updated)
  AND entity_id = 'number.boiler_heating_temperature'
  AND state ~ '^[-0-9.]+$'
UNION
(SELECT
   now(),
   state ::decimal as "heating temp"
 FROM states
 WHERE
   entity_id = 'number.boiler_heating_temperature'
   AND state ~ '^[-0-9.]+$'
 ORDER BY last_updated DESC LIMIT 1)
ORDER BY 1

but I hope there is an easier (nicer) way to handle this particular kind of graphs.

4

The question should be extended to ‘how to display values that fall outside of the selected region’.
For example, a particular setting changes to 40 on november 20 08:00 and to 50 on november 25 21:00. When a graph is displayed for the period november 22 0:00 - 24:00 nothing is displayed as there are no data points. The setting does have a value in this period, 40, and when using a line type graph it should be possible to show a horizontal line at 40 spanning the region.