Direction of trend arrow does not match actual trend

[StoicTheVast]

Hi there,

Thanks for the cool app.

Dexcom G6, Samsung Note 8, xDrip+ 2024.10.11

I have sometimes observed the direction of the trend arrow does not match the actual trend, but today I captured a particularly egregious example. I felt like I was getting low, checked the app summary notification and saw it said 4.6 and steady. I was about to dismiss my feeling but then thought I would double-check the detail graph, and saw it was in fact falling steadily, fast enough that it was predicting a low in 51 mins (which did occur, sooner in reality).

I'm not sure the criteria for determining the trend arrow, but if the blood sugar was falling fast enough for it to be predicting a low soon with the dotted line, then that seems like a good reason to make the trend arrow to be falling, rather than steady.

Can I ask for a confirmation if the trend arrow direction is behaving as expected? If perhaps the blood sugar wasn't falling fast enough for some people to want the trend arrow to show falling, would it be possible to include a sensitivity option so it can be personalised?

Thanks

[jonprogers]

Have you found the 'Graphical Trend Arrow' functionality?

https://navid200.github.io/xDrip/docs/Display/TrendArrow.html

I use this and find that it gives me a much finer view of the change between the last two readings than the standard arrow...

I think that a fall of 0.2mmol/l/5min is regarded as steady although someone with more experience will probably confirm (dexcom define 'steady' as less than 1mg/dl/min which is 0.28mmol/l/5min)

[StoicTheVast]

Hi Jon.

Nope, I had not found that functionality. I was bemused it should be hidden that way, but on your recommendation I gave it a shot to see how it worked for me. I found it did give a more nuanced arrow direction, which was good, but unfortunately that did not get picked up by the summary notification area, so now the arrows are inconsistent. I don't think that inconsistency will work for me, so I probably won't keep it enabled. Here's an example of the inconsistency:

Thanks for your information about the fall rates, it looks like it was not quite fast enough to be flagged. I'm not sure exactly what the algorithm is to decide when to display the red trendline warning, it seems like it might be fairly complex, but I am finding it's pretty much on the money - it's rare for me to feel like I'm getting low without there being a trendline warning, and it's rare for there to be a trendline warning when I'm not feeling like I'm getting low. I'd be happy for the app to use that same trigger to point the arrow downwards, if that were possible. If not, I'm learning more how to use the app and where and how to interpret and trust its results...

Thanks again.

[Navid200]

The red dotted line is Momentum. It's what xDrip uses for extrapolating readings.
You can enable a forecast low alert that uses it:
https://navid200.github.io/xDrip/docs/Alerts/ForecastLow.html

The trend arrow that xDrip shows on screen is calculated using the current and previous reading. Graphics trend arrow has a higher resolution. Either way, the trend arrow that xDrip shows on screen is what it calculates using the current and previous reading.

The trend arrow that xDrip broadcasts is what it receives from the data source.
For example, if you use xDrip to collect from a G7, the trend arrow xDrip broadcasts is the trend arrow it receives from G7 and you can see it by enabling data tables as well: https://navid200.github.io/xDrip/docs/Datatables.html

There have been requests to change this so that what xDrip broadcast and what it shows agree.
We cannot do that.
As an xDrip user, I would like xDrip to report to me a deviation as soon as possible. If a manufacturer decides to delay their reports in order to avoid noise at the cost of delaying a real deviation, I don't want xDrip to follow suit.

[jonprogers]

As an xDrip user, I would like xDrip to report to me a deviation as soon as possible. If a manufacturer decides to delay their reports in order to avoid noise at the cost of delaying a real deviation, I don't want xDrip to follow suit.

I'd certainly second this view, it's one of the advantages of xDrip over the manufacturer app for me.