Figure 1.

The two complementary methods of understanding a transcription profile. (a) Two transcription profiles of three genes are shown. Rows form gene vectors while columns form experiment vectors. (b) In a typical profile comparison, gene vectors are plotted in two dimensions, where the axes represent the experiments and the points are the genes. Data from (a) are plotted. Additional genes add points to the graph, but it remains in two dimensions. (c) In the vector-based approach, the axes are genes and the points are experiments. Data from (a) are also plotted here. Additional genes would not add any points to the graph (that is, there would always only be two vectors), but the space that the vectors reside in would increase in dimension.