@TrystanLea - definitely one for you.
I’ve noticed some peculiarities in the graphing recently.
Apologies, I will get on to this
Thanks Trystan 
Here’s another example to consider. Here are some graphs of the temperature feed from my new emonTH. I’ve used point display so it’s easy to see what data is actually being displayed. All I’ve changed between the graphs is the timescale (visible in the graph and the snapshot names):
Here’s what the data file looks like:
data/phpfina/71 metadata
id: 71
npoints: 0
interval: 5
start_time: 1699789110 2023-11-12 11:38:30
2023-11-12 11:38:30 19.100000 19.1000003814697
2023-11-12 11:38:35 NaN NaN
2023-11-12 11:38:40 NaN NaN
2023-11-12 11:38:45 NaN NaN
2023-11-12 11:38:50 NaN NaN
2023-11-12 11:38:55 NaN NaN
2023-11-12 11:39:00 NaN NaN
2023-11-12 11:39:05 NaN NaN
2023-11-12 11:39:10 NaN NaN
2023-11-12 11:39:15 NaN NaN
2023-11-12 11:39:20 NaN NaN
2023-11-12 11:39:25 19.100000 NaN
2023-11-12 11:39:30 NaN NaN
2023-11-12 11:39:35 NaN NaN
…
2023-12-01 15:48:00 NaN NaN
2023-12-01 15:48:05 NaN NaN
2023-12-01 15:48:10 20.600000 NaN
2023-12-01 15:48:15 NaN NaN
2023-12-01 15:48:20 NaN NaN
2023-12-01 15:48:25 NaN NaN
2023-12-01 15:48:30 NaN NaN
2023-12-01 15:48:35 NaN NaN
2023-12-01 15:48:40 NaN NaN
2023-12-01 15:48:45 NaN NaN
2023-12-01 15:48:50 NaN NaN
2023-12-01 15:48:55 NaN NaN
2023-12-01 15:49:00 NaN NaN
2023-12-01 15:49:05 20.600000 NaN
2023-12-01 15:49:10 NaN NaN
2023-12-01 15:49:15 NaN NaN
2023-12-01 15:49:20 NaN NaN
2023-12-01 15:49:25 NaN NaN
2023-12-01 15:49:30 NaN NaN
2023-12-01 15:49:35 NaN NaN
2023-12-01 15:49:40 NaN NaN
2023-12-01 15:49:45 NaN NaN
2023-12-01 15:49:50 NaN NaN
2023-12-01 15:49:55 NaN NaN
2023-12-01 15:50:00 20.600000 NaN
2023-12-01 15:50:05 NaN NaN
2023-12-01 15:50:10 NaN NaN
2023-12-01 15:50:15 NaN NaN
2023-12-01 15:50:20 NaN NaN
2023-12-01 15:50:25 NaN NaN
2023-12-01 15:50:30 NaN NaN
2023-12-01 15:50:35 NaN NaN
2023-12-01 15:50:40 NaN NaN
2023-12-01 15:50:45 NaN NaN
2023-12-01 15:50:50 NaN NaN
2023-12-01 15:50:55 20.600000 NaN
2023-12-01 15:51:00 NaN NaN
2023-12-01 15:51:05 NaN NaN
2023-12-01 15:51:10 NaN NaN
2023-12-01 15:51:15 NaN NaN
2023-12-01 15:51:20 NaN NaN
2023-12-01 15:51:25 NaN NaN
2023-12-01 15:51:30 NaN NaN
2023-12-01 15:51:35 NaN NaN
2023-12-01 15:51:40 NaN NaN
2023-12-01 15:51:45 NaN NaN
2023-12-01 15:51:50 20.600000 NaN
2023-12-01 15:51:55 NaN NaN
2023-12-01 15:52:00 NaN NaN
2023-12-01 15:52:05 NaN NaN
2023-12-01 15:52:10 NaN NaN
2023-12-01 15:52:15 NaN NaN
2023-12-01 15:52:20 NaN NaN
2023-12-01 15:52:25 NaN NaN
2023-12-01 15:52:30 NaN NaN
2023-12-01 15:52:35 NaN NaN
2023-12-01 15:52:40 NaN NaN
2023-12-01 15:52:45 20.600000 NaN
2023-12-01 15:52:50 NaN NaN
2023-12-01 15:52:55 NaN NaN
So the data is in the file, but the graph isn’t displaying it.
I don’t understand why the file (PHPFINA) has so many NaNs in it. The data should be every minute. I don’t understand why it’s recording nulls every five seconds?
edit: to add that the second NaN on each line is a difference of the first value on the line from the previous first value. So it normally shows the difference between successive values but here it’s useless.
PS the forum seems to be attributing the wrong date to this comment - it should be 1 Dec.
The feed was created with an interval of 5 seconds, so has nulls between each recorded value.
I’m afraid I still don’t understand. How is the feed interval set? I don’t seem to have any control over it, so why isn’t it set automatically to the same interval as the device? I don’t see anything about feed interval when creating a feed.
Another graph weirdness. I was playing about investigating histograms. Looking at the pizerow:humidity feed I mentioned before, for example, if I look at the “Time at value” histogram then the tooltips say things like
Node pizerow:humidity
8280.0 °C
Thu, 1 Jan 1970 01:00
(0.0947)
where the histogram appears to be showing an x-value of 94.75 and a y-value a bit above 8000. I can see that the temperature value presumably corresponds to the y-value and the number in brackets corresponds to the x-value, but what’s the date, why are the units all wrong etc? (I suppose the x-values are the humidity %, and yes the units for that feed are set to %)
How does it know? “The device” could be anything, sending data at whatever rate a third party decided it should. EmonCMS cannot know what that is.
On the Inputs page:
Also when clicking on New feed button on Feeds page:
…though the minimum (on my instance) is 10s, so I don’t know how you managed to create a 5s feed.
In this case it chose the name emonth5 by itself, so it thinks it knows what the device is! And it knows what rate that device sends data. I agree in the general case of inputs like those I post using HTTP.
I wish you would post the whole page instead of clipping little bits so I don’t know what I’m looking at. I assume it’s from the same place I snapped this:
in which case I don’t see what you see!
I’ve never even noticed that facility is there, let alone used it!
… which may account for why the minimun there doesn’t seem to apply.
That is the right place, but you are choosing an existing feed. You cannot change a feed that already exists, neither on that page nor anywhere. The mechanism whereby the data is stored makes any change impossible. You can only set the Feed Interval when creating a feed. If you want to change the interval, you must create a new feed and then import the old data, either repeating, interpolating or selecting data points as necessary. I’m not aware of the details how to achieve this.
There is or was a bug in the Feed Interval selection. If no interval is chosen, it has defaulted to 5 seconds, even though the option “5s” (which used to exist) has been removed. Trystan is aware and has or will soon correct this, the minimum will be 10 s.
Just to confirm, how are you looking at this data?
No, I’m not. That is why it says: “You have no processes defined”! I believe it’s a[nother] bug in the UI.
Using a perl program I wrote to examine it.
Is there anybody who can enlighten me on how to do this? Or do I write another perl program to do it?
Ah PERL, not used that for a long time. Care to share?
It’s nothing to do with GitHub per se, more that this is not being pulled in by ReadTheDocs AFAICS @Gwil. ReadTheDocs is only being told to pull in the User Guide and not the other 2 folders 
That Badger set has thrown up an original Fork of the Learn Repo so you can see what it was like a while back 
There are other Forks available 
The current info looks the same as the old Learn from a quick scan (last updated in 2021 it seems).
OK, you’re not. Perhaps.
When you choose CREATE NEW, you can name the feed, choose the feed engine and set the feed rate. If you choose a feed on the drop-down list, it already exists (otherwise it wouldn’t be on the list, would it?). I’ve already told you, you can’t change a feed after it has been created. If you choose an existing feed, you can’t see the feed engine to change it, you can’t see the feed interval to set or change it because you’re not allowed to change the feed engine or the feed interval of a feed once it has been created.
I’m quite certain there will be someone who can help you, it’s just that I don’t know all that much about emonCMS, especially the internals.