Lovelace sensor graph accuracy

[ghost]

@SteveEdson commented on Nov 10, 2018, 11:25 PM UTC:

Home Assistant release with the issue:
0.82 (and previous versions)

Last working Home Assistant release (if known):
N/A

Operating environment (Hass.io/Docker/Windows/etc.):
Docker

Component/platform:
Lovelace Sensor card

Description of problem:
The graph in lovelace shows one thing, but clicking on the entity shows a very different graph. I'm not sure how accurate the data is in the lovelace card, as it looks very different to what I would expect.

Problem-relevant configuration.yaml entries and (fill out even if it seems unimportant):

- type: sensor
  name: Heating
  id: house_temperature
  entity: sensor.house_temperature

Expected, from normal graphs:

Lovelace card:

As you can see, they are very different.

This issue was moved by cgarwood from home-assistant/home-assistant#18366.

[Ernst79]

Having the same issue. I thought it was by design. Increasing the accuracy doesn’t help much unfortunately.

[Petro31]

So i'd like to comment here, the default accuracy is 10. This graph does not average points, it purely pulls data points. So if your history over 24 hours has 40000 data points and the accuracy is 10, the graph will show every 4000th data point. If you want an accurate representation, you may need to bump the accuracy up ten fold if your sensor collects a ton of data.

[SteveEdson]

Does it show every 4000th data point, or take the average of the data points in groups of 4000?

[Petro31]

Simply just shows the 4000th data point. No averaging. It also plots the array with equal x spacing. I.E if you have large time gaps in your data, they won't be represented properly.

[SteveEdson]

Ok, surely it'd make sense if these data points were averaged out then? Or at least have the option to do this?

[Petro31]

It's doable. I just made an update to the card and purposely avoided that because the data points from history are not guaranteed to be uniformly spaced. So a moving average would also doctor the graph just as much as leaving it be.