(a) Pairs of points satisfying a threshold value of d (see Methods ) greater then 0.2. Seven pairs (s = 7; connected by blue lines) are selected for the following steps. The green line is the true functional representation of X2 versus v3, which in an actual situation is not known. (b) Pairs in (a) are merged, based on the distances between points in each “node” and the distances between two points in a pair. (c) Subgroups of pairs in (b) are merged. (d) If the value of v3 is known for X2 = 1 or for some other value. The entire cluster of lines is vertically shifted accordingly. If small values of X2 are covered by the pairs, the shift is determined by the observation that a flux is usually zero if the substrate concentration is zero. Here, the sum of errors between the estimated points and corresponding points on the true green line is 0.0354.