Middle-error-rate (MED) datasets. (A) shows the ratio of the read count of the untrimmed reads over that of the trimmed reads by all tested trimmers applied to the simulated MED/dMED datasets. (B, C) illustrates the length distributions of the trimmed reads processed by each of the tested adapter trimmers applied to simulated MED (B) and dMED (C) datasets. The distributions are depicted with the ratio of the amount of reads trimmed at certain length, ranging from 1 to 100 bp, over the total amount of trimmed reads. The ratios are magnified by 5 times with the range from 1 to 50 to visualize the presence of short fragments after trimming.