FA-97413 / Knitting and sewing pattern grading / Member archive
Yarn yardage estimator: area ratio · case 03
A whole sweater is estimated at a fraction of a gram.
Case contract
grams = garment_area / swatch_area * swatch_g; meters = grams * skein_m/skein_g; add margin_pct as a multiplier (meters*(1+margin/100)). skeins = ceiling(meters/skein_m); leftover = skeins*skein_m - meters. Return [meters, skeins, leftover] with meters and leftover half-up integers. Non-positive swatch area or skein weight -> "error: swatch".
Why this case matters
Designers and knitters estimate how many skeins to buy from a weighed swatch.
One recorded failure
Sample boundary fixtureThis sample comes from the broken implementation of a controlled reproducer.
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| exact two skeins | [1, 1, 199] | [400, 2, 0] | Failed |
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