作者subtropical (风大雨大)
看板BioMedInfo
标题[问题] N50
时间Wed Sep 9 14:08:59 2009
关於genome在做assembly时,paper都会提到N50 size为多少。
这是网路上我所查到的定义:
http://www.cbcb.umd.edu/research/castats.shtml
The N50 size of a set of entities (e.g., contigs or scaffolds) represents the
largest entity E such that at least half of the total size of the entities is
contained in entities larger than E.
For example if we have a collection of
contigs with sizes 7, 4, 3, 2, 2, 1, and 1 kb (total size = 20kbp), the N50
length is 4 because we can cover 10 kb with contigs bigger than 4kb.
我的解读是占50%的contig, 所以20kbp的N50应该是10kbp
不过看了下面的例子又明显不是这样...
请问N50的定义到底该怎麽下呢?
谢谢不吝解惑.
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1F:推 huggie:因为大於4 kbp 的 contigs 有 7 跟 4 加起来超过20kbp的 09/09 16:54
2F:→ huggie:一半,因此这个例子内N50是4 kbp。并非每个加起来20kbp的 09/09 16:55
3F:→ huggie:例子都会是4 kbps 09/09 16:55
4F:→ subtropical:为何不是7kbp呢@@? 09/09 17:17
5F:推 huggie:7 kbps < 10 kbps 所以不是 7 09/11 14:14
6F:→ subtropical:原来如此!谢谢h大! 09/14 10:02