Image matrix of discriminative weight functions derived from trained classifiers based on the trimer kernel. Each of the 64 lines shows the values of one trimer-specific weight function obtained from an average over 50 runs (see text). Each of the 200 columns corresponds to a certain position with 0 indicating the position of the start codon. The function values are visualized by the color of the corresponding matrix elements. The complete matrix of function values has been scaled to yield a unit maximum which is located at the ATG line at position 0. For noise reduction all matrix elements with an absolute value below 0.1 have been zeroed. In general, maxima and minima indicate discriminative features which contribute to the prediction of positive (true) and negative (false) TIS, respectively. Note that the region of discriminative features is rather small and mainly concentrated around the start codon on the left (upstream) side of the image.