Alexander Heldt
9e47aa53ff
The caption read like "down about 329 g a week — roughly 460 g a day then, 320 g a day now". Subtract the two amounts and you get 140 g, not 329. The arithmetic behind it was self-consistent, but the sentence was not, and a caption a reader can disprove by subtracting its own numbers is wrong whatever the code was doing. The rate was slope x 7, while the line only covers the complete days in the window. Today is never fitted, being unfinished, so a 7-day window leaves at most five days and any marked day takes another — in this case about three. The rate was therefore stretched well past the days it was measured from, and the two endpoints, which were not, could never agree with it. It quotes the change between the two ends now, which is the one figure a reader can check: "down about 140 g — from roughly 460 g a day to 320 g." The change is derived from the rounded ends rather than from the slope, so the subtraction works exactly rather than to within the rounding. The weekly rate goes rather than being repaired. It cannot reconcile on a short window, and it only ever meant anything where the fit spanned a week or more — which is not something to leave as a trap for whichever window the reader happens to have picked. The check that let this through asserted the sentence contained certain phrases, not that its numbers agreed with each other. There is now one that parses all three figures back out and asserts the move is exactly the difference of the ends, across each window length; it fails against the old wording, which is the only evidence worth having that it would have caught this.
141 lines
6.4 KiB
JavaScript
141 lines
6.4 KiB
JavaScript
// The fit through the Food (grams) bars. The arithmetic is easy to get subtly
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// wrong and the result is a sentence stating a fact about the puppy, so the
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// cases that matter are the ones where it should decline to say anything.
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import { load } from "./extract.mjs";
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import { suite, eq, ok, report } from "./assert.mjs";
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const app = load({ names: ["foodTrend"] });
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const words = load({ names: ["foodTrendSentence"] });
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// The 7/14/30 picker reaches the trend by deciding how many days weeklyData
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// builds — there is no second mechanism, so this is the thing to hold still.
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let windowDays = 7;
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const weekly = load({
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names: ["startOfDay", "endOfDay", "ymd", "weeklyData"],
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stubs: {
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chartDays: () => windowDays,
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isExcluded: () => false,
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eventsForDay: () => [],
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sleepMsInRange: () => 0,
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walkMsInRange: () => 0,
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},
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});
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suite("the day picker is what sets the trend's window");
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for (const n of [7, 14, 30]) {
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windowDays = n;
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eq(weekly.weeklyData([]).length, n, `picking ${n}d gives the charts ${n} days to fit over`);
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}
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windowDays = 7;
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// weeklyData's shape, as far as foodTrend reads it. Today is last, as there.
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const days = (grams, { excluded = [] } = {}) =>
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grams.map((g, i) => ({ grams: g, excluded: excluded.includes(i) }));
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suite("it declines to fit when there is nothing to fit");
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{
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eq(app.foodTrend(days([300, 320, 310])), null,
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"three days is too few — today is dropped, leaving two, and two always fit perfectly");
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eq(app.foodTrend(days([300, 320, 310, 330, 340], { excluded: [0, 1] })), null,
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"marked days don't count toward the four either");
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eq(app.foodTrend(days([])), null, "an empty window fits nothing");
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}
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suite("today is left out, being half-eaten");
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{
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// Four steady days then a partial today. Including today would tip the line
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// down; the fit should not see it at all.
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const t = app.foodTrend(days([400, 400, 400, 400, 50]));
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ok(t, "four complete days are enough");
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eq(Math.round(t.change), 0, "a flat run stays flat despite today being low");
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eq(t.last, 3, "the line stops at the last complete day, not at today");
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}
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suite("it reports a direction only when the climb beats the scatter");
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{
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const rising = app.foodTrend(days([200, 250, 300, 350, 400, 450, 0]));
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ok(rising.clear, "a clean climb is reported");
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eq(Math.round(rising.change), 250, "…as the move across the five days it fitted, 200 g to 450 g");
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const falling = app.foodTrend(days([450, 400, 350, 300, 250, 200, 0]));
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ok(falling.clear, "a clean fall is reported");
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ok(falling.change < 0, "…with a negative change");
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// Same mean, no direction, plenty of noise: the honest answer is "steady".
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const noisy = app.foodTrend(days([200, 500, 210, 480, 190, 520, 0]));
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ok(!noisy.clear, "a see-saw is not a trend, however the slope comes out");
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// A gentle real climb buried in large day-to-day swings: also not claimable.
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const buried = app.foodTrend(days([300, 520, 180, 540, 200, 560, 0]));
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ok(!buried.clear, "a slope smaller than the scatter is not reported as a trend");
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}
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suite("the fitted line passes through the data");
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{
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const t = app.foodTrend(days([100, 200, 300, 400, 500, 0]));
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eq(Math.round(t.at(0)), 100, "it starts where the first day sits");
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eq(Math.round(t.at(4)), 500, "and ends where the last complete day sits");
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eq(Math.round(t.mean), 300, "the mean is the mean of the days it fitted");
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}
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suite("marked days are skipped without shifting the line");
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{
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// The middle day is marked; the rest describe a clean 50 g/day climb. The fit
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// must ignore the hatch rather than reading it as a day of zero grams.
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const t = app.foodTrend(days([200, 250, 0, 350, 400, 450, 0], { excluded: [2] }));
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eq(Math.round(t.change), 250, "the climb is unchanged by the marked day");
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ok(t.clear, "…and it is still clear, not drowned by a false zero");
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}
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suite("what the sentence is allowed to say");
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{
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const say = (grams, opts, win = 14) => words.foodTrendSentence(app.foodTrend(days(grams, opts)), win);
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const rising = say([200, 250, 300, 350, 400, 450, 0]);
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ok(/up about 250 g/.test(rising), "a clear climb gives the size of the move");
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ok(/from roughly 200 g a day to 450 g/.test(rising), "…and the figures at each end");
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ok(/the last 14 days/.test(rising), "…named against the window it was fitted over");
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// The defect this replaced: the move was quoted per week while the fit spans
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// at most five days on a 7-day window, so the figure and the two endpoints
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// disagreed and a reader who subtracted them found the sentence wrong.
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// Whatever the window, the three numbers in the sentence must reconcile.
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for (const [label, grams, win] of [
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["a steep 7-day fall", [460, 425, 390, 355, 320, 285, 0], 7],
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["a long 14-day climb", [200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 420, 440, 0], 14],
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["a gentle 30-day climb", [...Array(29).fill(0).map((_, i) => 300 + i * 12), 0], 30],
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]) {
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const s = say(grams, undefined, win);
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const m = s.match(/about (\d+) g — from roughly (\d+) g a day to (\d+) g/);
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ok(m, `${label}: the sentence has all three figures`);
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if (m) {
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const [, moved, from, to] = m.map(Number);
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eq(moved, Math.abs(to - from), `${label}: the move is exactly the difference of the two ends`);
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ok(new RegExp(`is ${to > from ? "up" : "down"} about`).test(s),
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`${label}: and the direction matches which end is larger`);
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}
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}
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const steady = say([300, 302, 298, 301, 299, 300, 0]);
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ok(/roughly steady/.test(steady), "a flat run is called steady");
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ok(/averaging about 300 g a day/.test(steady),
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"…and quotes the average, which is a measurement rather than model output");
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ok(!/then/.test(steady) && !/ now\b/.test(steady),
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"…but not fitted endpoints, which would dress up a line nobody should read");
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const noisy = say([200, 500, 210, 480, 190, 520, 0]);
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ok(/roughly steady/.test(noisy) && /variation is larger/.test(noisy),
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"a see-saw says the variation beat the trend, rather than quoting a slope");
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const none = say([300, 320, 310]);
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ok(/Not enough complete days/.test(none) && /needs four/.test(none),
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"too few days explains itself instead of leaving the chart bare");
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// False precision would make a fit look like a reading.
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ok(/\b\d*[05] g a day/.test(rising), "figures are rounded to 10 g, not quoted to the gram");
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const falling = say([450, 400, 350, 300, 250, 200, 0]);
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ok(/down about/.test(falling), "a clear fall says down");
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}
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export default report("food-trend");
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