slope: the least-squares slope of the points the readings are (spec/04 §5): a number
v at place i is the point [i, v], a reading [x, y] (or {x, y}) the point
itself. nil for fewer than two points, or when every x is equal.
slope: the least-squares slope of the points the readings are (spec/04 §5): a number
v at place i is the point [i, v], a reading [x, y] (or {x, y}) the point
itself. nil for fewer than two points, or when every x is equal.