The daily grams bars bounce around enough to hide a steady climb, so they
cannot answer the question you actually have about a growing puppy: is he
eating more than he was? A least-squares fit through them can.
Two kinds of day stay out of the fit. Today is half-eaten, and including it
would pull the line down every morning and let it drift back up as meals go in
— a line that tracks the clock rather than the dog. A day marked "not counted"
has a hatch rather than a figure, and fitting a zero there would invent a dip.
The line is drawn only across the days it was fitted on, so it never implies it
knows about the ones it skipped.
The caption is the part that needed the care. A straight line through seven
noisy points will always have a slope, and announcing it as a fact is the same
mistake the walking goal made. So a direction is named only when the fitted
climb is larger than the scatter of the days around it, and only when it clears
5 g a week and a twentieth of a typical day; otherwise it says the variation is
larger than any trend, which over a short window is usually the truth.
It names its window too — "over the last 14 days" — because the 7/14/30 picker
already drove this (weeklyData builds the array the fit runs on) but nothing on
screen said so, and the line moves too little between windows to show it. When
there are fewer than four complete days it now says why there is no line rather
than leaving bars with nothing through them.
Meals can be logged without an amount, so the note counts them: a day can read
low because he ate little or because nobody typed the number, and the chart
should not let those look the same.
The checks cover the refusals rather than the arithmetic — a see-saw is not
reported as a trend, a slope under the scatter is not either, three days will
not fit, a marked day does not shift the line, and each window length reaches
the fit intact.
Alexander Heldt
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