Use the purple line (weighted moving average) to determine lane position
It is frustrating that one single weigh-in, unusually high for whatever reason, can derail the entire goal and freeze my graph. I LOVE the purple line, and its position within the yellow brick road is what I plan to monitor. I wish the purple line average, and not that individual day's weigh-in, was the determining factor for whether I'm in the right or wrong lane, or above or below the road. An unusually high weigh-in (above the road) would affect the purple line, but most likely not enough to derail within one day. At least it would be nice to have the option to choose between methods of determining lane position?
I wrote an Official Rebuttal here: http://blog.beeminder.com/movingav/
But also we’re working on a replacement of the smart (ie, too clever for its own good) auto-adjusting width of the Yellow Brick Road that we hope will better get at the fundamental problem. Stay tuned, and keep the feedback coming!
Bryan Kennedy commented
I think that the better way to do this is to allow for an extra field on a data point. This field would allow you to mark the data point as recorded, but prevent it from counting towards your goal (aka it can't derail you). This could be a scarce commodity. Maybe you only get to use it once every few weeks. But that way you can still track the data point, but don't count it towards derailing. You'd be on the hook to get your weight down below the goal for the next period.
I'm sure people do this from time to time already by deciding to either not step on their scale, or stepping on it and stepping off before it has time to send the data along to Beeminder.
Admindreeves (Cofounder, Beeminder) commented
Quoting myself from the Akratics Anonymous discussion:
The moving average is the right thing to look at to see the trend but I don't think it will help to beemind it. Here's my concen...
Imagine your road is sloping down and you're below it at first but you weigh in every day at the same weight, 100kg. You're on a collision course with the road. After 9 days of 100kg each day, you find yourself on the wrong side of the road. It's an emergency day and you need to lose .5kg to get back on. Except you're beeminding the moving average so now you need to lose 10 times that (or whatever) to actually bring the average down enough. You're actually requiring a bunch more foresight to keep from derailing, which I think is a nonstarter. In general, being akratic and beeminding the moving average still means that you're skating the edge and every day there's some magic weight that you must weigh in at to keep from derailing. That's fundamental to beeminding weight. No matter how you try to smooth the data or widen the road, if you eked by yesterday then there will necessarily be a magic weight that you absolutely must hit today to stay on track. It's like a no-free-lunch theorem. Whatever we do ends up equivalent to having a single bright line that your (actual) weight is not allowed to cross every day.
There's a pertinent and related discussion on Akratics Anonymous.
The more I think about this, the more it bugs me! Also, this might be due to the fact that I just experienced a fluctuation that had me below the road yesterday (yay!) and then in the wrong lane today (oh no!). The reason I love the purple line is that it's not so volatile, and I think of it as where my "true" measurements are. Granted, I realize the purple line necessarily lags a bit, because it's factoring in previous days' measurements, but I'll take that over the day-to-day rollercoaster. So yes, I wish we could at least choose to have the purple line be the focus of our graph, and position within the yellow brick road. Here's a look at the aformentioned fluctuation (Aug 23/24): https://www.beeminder.com/healthygroove/goals/bodyfat