N50

N50 is a widely used metric for mearing the quality of contigs outputted by the assembly algorithms. Some of the definitions or descriptions on N50 are listed as follows:

 

"In addition to total size, the N50 size is a very useful statistic for comparing genome assemblies: it represents the size N such that 50% of the genome is contained in contigs of size N or greater.  "-- Genome Biology, "A whole-genome assembly of the domestic cow, Bos taurus".

 

"In other words, N50 is the contig length such that using equal or longer contigs produces half the bases of the genome."

　　　　--wikipedia, http://en.wikipedia.org/wiki/N50_statistic

 

Other useful links:

A thread in SEQAnswer: http://seqanswers.com/forums/showthread.php?p=41420

http://genomics-array.blogspot.hk/2011/02/calculating-n50-of-contig-assembly-file.html