Singleton

This feature allows users to report singleton reads to an alignment file for further inspection (e.g. alignment to the genome, blast analysis to detect possible contaminants, etc.). The analysis of singleton reads (number, origin) is a part of a typical assembly assessment process ([1](http://sourceforge.net/p/trinityrnaseq/mailman/message/31970036/), [2](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3733778/)). This option allows users to further investigate the origin of the singleton reads.