Apple is terrible at math

by Volker Weber

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Activity rings are a great motivation to stay active. I have closed them for years, every single day. But with the latest major watchOS update Apple introduced new challenges, and they are complete and utter b/s. Current example:

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That is quite obviously a calendar problem. This average will go down to more sensible levels and at the end of the month I will not earn this award, no matter how many calories I burn, since the math is broken. It's not the only place that is completely wacky. Compare these three numbers:

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Looking good. How many weeks can I have been awarded all three goals? Max 141, only if I failed Exercise in the same week as Move. Otherwise it would be 140. Apple however awards me 188 weeks of reaching all three goals.

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188 weeks times 7 days is 1316 days. 25. Feb 2018 minus 1316 days is 20 Jul 2014. I have had my Apple Watch since the end of June 2015, once month after it was officially released. I have to assume they started testing in June 2014 and those "reaching all activity goals" is actually pretty accurate for me, since I started my #dontbreakthechain program in the spring of 2014, tracking into Apple Health with all kinds of of fitness bands. It would save my life three years later. For that I am forever grateful.

If I could only switch off these extra challenges. They are messing up a neat history.

InkedIMG 2469 LI


13:37 for the second time. Coincidence? I think not!

Frank Quednau, 2018-03-01

I just checked my counts.

My week counts are correct:
147 Move weeks
147 Expertise weeks
146 Stand

146 All Activities weeks.

So all fine here .

Apple is replacing placeholders from a text module to show you the Week Challenge message.
It looks like, that the two placeholders in the text module have been swapped in your chosen language. Looks like a localisation bug.
I have set German for myself. The text and values for the Week Challenge are correct.

May there is one or more logged health entries from the past which screws it up.

By the way:
The extra challenges keeps your neat history to look better.
You would like to remove the silver ones not the gold ones, right?
So the 10.2017 would be gone.
(Just kidding - I know you were sick that month)


Detlev Pöttgen, 2018-03-01

Ups, I just noticed you have maybe another March Challenge:

Mine is:

"..., wenn du diesen Monat einen Kalorienverbrauch von mindestens 28.112 Kilokalorien erreichst! Bisher hast Du 584 Kilokalorien verbraucht!"

Detlev Pöttgen, 2018-03-01

Messed up on my watch too. Never changed language. Looks like there’s no way to launch a “recompute”.

Stephan Wissel, 2018-03-02

Funktioniert bei mir auch nicht richtig. Im Februar sollte ich 1 Kalorien(!) verbrauchen um das ziel zu erreichen. Hab ich leider nicht geschafft. Diesen Monat soll ich in Summe 17.916 Kalorien verbrauchen. Angeblich hab ich davon schon 14.281 erreicht. Dabei hatte ich Gestern eher einen ruhigen Tag mit 500 Kalorien laut Tagesübersicht.

Moritz Dahlmann, 2018-03-02

The problem is that the calculations are looking at the whole month and don't do a scaling to the days that have actually passed.

So for a x calories this month, they look at the data so far (500 kCal) multiply it with 31 and arrive at 15'500. The data get's more accurate as the month gets older.

Same for on average x calories per day - the data becomes more plausible as the days over moves towards the amount of days per month.

Still there are obvious bugs - last month I had a "average x calories / day" challenge, I slacked on a few days and still got in above average (maybe because February only had 28 days?)

Even though I can explain what is shown, it is still a disgrace and totally weird. Wonder how that got through testing...

Jens-Christian Fischer, 2018-03-02

It is actually much simpler than any of your theories. It is a typical programming error: off by one.

It takes last month's performance and applies it to this month. Example: when it says you reached 18000 cals on day 1, it will say you reached 9000 on day 2, 6000 on day 3 and so forth. It divides CalorieSum(last month) by days(this month) instead of CalorieSum(this month) divided by days(this month) to get to an average.

This is also the reason why everybody who met the January challenge in December got their January reward on day one.

What boggles my mind is that Apple cannot figure this out and apply a very simple fix.

Volker Weber, 2018-03-02

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