Transcriptional module identification: discretization and alphabet transformation.

<p>Illustrative example of discretization and alphabet transformation for a time series gene expression matrix: (left) original expression matrix <i>M</i>'; (center) discretized matrix <i>M</i>, obtained by applying a discretization based on transitions between time points to the original matrix <i>M</i>' using a three-symbol alphabet <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035977#pone.0035977-Ji1" target="_blank">[28]</a>; and (right) matrix <i>M</i> after the alphabet transformation that appends the column number to every symbol in the matrix.</p>