history-graph could be more meaningful with fixed scale option

[pooh22]

The current history-graph card doesn't seem to have the option to define a fixed scale, eg min=0 max=2, to define the bottom and top values in the graph. Even better would be min="value at left time" and max="value at left time"+2

Specific use-cases would be where the graph plots something that you consume (power, water, heat) and you expect certain normal usage values. Unless there's really unusual behaviour, the graph plots a more or less straight line from bottomleft to topright because the ranges are derived from the data.
This doesn't give me more information than that the meter-reading is working (good to know!), but what would help me understand the usage, would be to set limits for how much is to be expected normally, then I can see how fast or slow the usage is over the day. And if it's a high usage or low usage day, for example.

So for a history graph with a constantly growing datasource, it would make sense to define a value range per timeperiod and use that to define the vertical range of the graph displayed. For other types of graph a fixed min/max value may be more suitable, but I can't think of an example right now.

[pooh22]

I mean something similar, but e.g when you are plotting the value of the gas, or in my case heat, meter, it continually grows, so it's at 32 and grows by 0.1 per day (or something). The graph would look like a straight horizontal line if you just put minimal value of 0.

To continue with the heat example. In winter the usage per day is like 1GJ per day, but in summer only 0.010 GJ, but in the current graph, both look almost the same. When the graph for 1 day would have a maximum vertical range of 1 or 1.5 GJ, you can spot immediately if it's summer or winter from the graph. Better still, you could spot differences in usage patterns better, because it is more to scale of the expected.

[pooh22]

in the mini-card-graph there is a parameter: min_bound_range_secondary, which looks like it might fit my issue, though I haven't tried it yet and the implemented in version 0.x.x appears to imply it will be implemented at some time in the future.

The option to plot a second graph with the minimum boundary doesn't solve my problem (0 is so far out of range the graph will be a straight horizontal line at the top). Perhaps if I manually adjust the value every few days, but I'm not going to do that, I expect ;-)

I hope something like a bound range option can be added to the history-graph card, I think it would be a useful option to have for values that represent a consumption like energy/heat/water which can have a predetermined expected maximum consumption rate. It could even be used to help usage reduction targets by setting it lower than usual and try to stay below the value.

[Jojo-A]

I also think that an option to set upper and lower y-boundaries manually should be implemented into the standard history-graph card.
Of course auto-scaling is a good approach as a "first shot". But for meaningful interpretation it is essential to scale the desired signal into the "real world". While when you have only auto-scaling you might see only a zoomed version of the noise of the signal.
Example room temperature:
the actual value ranges from 19°C to 21°C. dT = 2°C. Relative to the interesting range of 10°C to 40C° this is ~6% "visual variation".
But the graph scales it in the range of 17°C to 23°C, which results in 33% "visual variation"! This is pointless.
A fundamental key competence when gathering data is to interpret them correctly. And this interpretation requires a meaningful reference system.