“…(An equivalent procedure can be used, for example, in spectroscopy for high-throughput screening, where the output is continuous and is the concentration of a substance of interest [Gilbert et al, 1997;Taylor et al, 1998b;Woodward et al, 1999].) The special power of GP, which we have found particularly valuable (Gilbert et al, 1997(Gilbert et al, , 1998(Gilbert et al, , 1999Jones et al, 1998;Taylor et al, 1998aTaylor et al, , 1998bGoodacre and Gilbert, 1999;Woodward et al, 1999;Goodacre et al, 2000;Johnson et al, 2000), stems from the fact that both the (potentially small number of) explanatory variables and the functional form of the relationship between them are evolved together. As suggested by a referee, and to avoid confusion, we note that genetic programming differs significantly from methods such as genetic algorithms.…”