Relative error against a key's true count, 4×64 sketch

Relative error against a key's true count, 4×64 sketch

One mark per distinct key in a Zipf stream of 60,000 items. The horizontal position is how often that key really occurred; the vertical is how far above the truth the sketch's estimate is, as a fraction of the truth. The fall is almost exactly a slope of −1, because the sketch's error is a fixed number of counts — about 2,548 here, being e/w of the whole stream — divided by whatever the key's own count happens to be. The heaviest key is over by 4.11% and the rarest by 34100%: the same sketch, the same query, and a factor of 8,290 between them.

Drawn at 700 × 420, wide on the page. Everything above is what error-against-frequency returns with no arguments; the caption is the generator's own, computed from the numbers in the drawing rather than written beside it.

5 essays call error-against-frequency. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the one its essay argues about — which is what optcheck and figfill exist to catch.