The line it crosses
A sum is only a number. A guess needs a decision. The rule compares the sum with a threshold, a fixed number. Here it is 40. The rule's answer is its verdict, call or wait. When the rule says call, it is said to fire.
- Gauge 6, days 1: the weighted sum is 40.
- 40 is at or past the threshold, 40.
- The verdict fires: call.
The rule
The sum is compared to one threshold. At it or past it, the rule calls. Under it, it waits.
At it or past it — even exactly on it — the rule calls. We state that direction, so nobody has to guess it.
Run the starter rule over every gauge reading and every day count. It calls on 28 of the 63 possible days. The line is where the sum equals the threshold. Those 28 days are on the line or beyond it. The other 35 days wait. They have not reached the line. The rule is only two multiplications and an add.
Slide the threshold below. An x marks a day where the rule calls. Watch the x cells move.
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