Discretization of the gene expression change.

If the change of the level of expression reported in Table 4 is larger than a given threshold T0, we write an arrow pointing upwards (↑), whereas if the change of the level of expression is smaller than −T0 then we write an arrow pointing downwards (↓). The symbol (—) indicates that no significant change was detected. In this example we used a threshold T0 = 1.5 to discretize the numbers given in Table 4.