Add delta option in aggregate_func

[PierreB49]

This option allows to show delta for instance to show daily or hourly consumption from cumulative data.

[maxwroc]

Hey, before addressing my comments please wait for @kalkih opinion.

Nice and simple extension please update documentation and give the example use case there (maybe update/mention this in the energy usage example)

edit:
BTW I don't know how come I didn't came up with this solution (my first change for this lib was actually to give a way to show the energy daily consumption). I think I was too focused on the getting the results form utility meter (not direct results from the sensor) :) Good job!

[PierreB49]

Hey, before addressing my comments please wait for @kalkih opinion.

Nice and simple extension please update documentation and give the example use case there (maybe update/mention this in the energy usage example)

edit:
BTW I don't know how come I didn't came up with this solution (my first change for this lib was actually to give a way to show the energy daily consumption). I think I was too focused on the getting the results form utility meter (not direct results from the sensor) :) Good job!

Thanks you for your reply. I'm a beginner in nodejs so there might be room for improvement in my code. I adapted the card for my usage and thought it could be useful for someone else.

[maxwroc]

Hey, before addressing my comments please wait for @kalkih opinion.
Nice and simple extension please update documentation and give the example use case there (maybe update/mention this in the energy usage example)
edit:
BTW I don't know how come I didn't came up with this solution (my first change for this lib was actually to give a way to show the energy daily consumption). I think I was too focused on the getting the results form utility meter (not direct results from the sensor) :) Good job!

Thanks you for your reply. I'm a beginner in nodejs so there might be room for improvement in my code. I adapted the card for my usage and thought it could be useful for someone else.

And it is awesome that you have decided to share the solution and update the lib!

One thing worth to mention additionally in the documentation is that it may not give exactly correct results. What I mean here is that in theory we should store somewhere the last state from previous time bucket and calc delta to the value from the next one. Here you calculate delta within single time bucket which in some corner case situations may produce incorrect results.
But anyway I think for majority of people this won't be a problem so I'm fine with this approach as the implementation is simple and does the job. It will be useful for people who don't want to add another sensor - utility meter.

I wonder what is @kalkih's optionion. I remember he didn't want to add similar functionality as it can be achieved via utility meter.

[kalkih]

Hello, this is indeed a nice addition to the card, thanks!
As Max said I've pointed people to utility meter when they've asked for functionality like this but I'm ok with this solution it's simple & could work fairly well in some configurations.

Just address the comments made by Max and add it to the documentation and I'll merge this, thank you!

[maxwroc]

You have edited little bit too much now ;) The local var name which I have asked to change was confusing because it wasn't containing graph coords and the name was exactly the same as the class property (so the impression was that the type of the value was the same - which was not true).
Class property this.histGroups doesn't contain grouped history values (as name suggests) but actually calculated graph points/coords. Please leave here the old name.

[maxwroc]

This probably covers requests: #197, #288

[maxwroc]

@kalkih can you merge this please? my last comment is a minor thing which we can do in another PR

[kalkih]

Great job, thanks for the contribution!

Needs to be added to the docs before next release.

[maxwroc]

Ok. Let me do it

[maxwroc]

#332