Correlation between AS frequency and EST coverage. The x-axis indicates groups of genes with certain numbers of ESTs. The primary y-axis for the bar graph indicates total number of genes within each group. The secondary y-axis for the line graph indicates the fraction of alternatively spliced genes for the group. Note that different bin sizes were used to keep the number of genes in each group greater than 500 in At and Os. AS data from groups with fewer than 80 genes in Mt were removed to reduce noise. Lj data were not shown as only the first six groups have more than 80 genes.