判断一个位点受到的是哪种选择压力

dN/dS = Nonsynonymous/Synonymous

http://www.chenlianfu.com/?p=3084
https://www.cnblogs.com/bio-mary/p/12923978.html

计算原理：
http://www.360doc.com/content/18/0318/11/19913717_738098289.shtml
http://www.360doc.com/content/18/0620/16/45962007_763872445.shtml

Note: dN/dS 并不能很好地区分 正向选择 和 选择力下降(限制下降) 两种情况
https://genesdev.cshlp.org/content/31/18/1841

https://genesdev.cshlp.org/content/31/18/1841
https://genesdev.cshlp.org/content/suppl/2017/10/19/31.18.1841.DC1/Supplemental_Methods_and_Text.pdf

dN/dS is a ratio of the number of nonsynonymous (replacement) substitutions per nonsynonymous site to the number of synonymous (silent) substitutions per synonymous site.

The usage of dN/dS is limited to protein-coding genes.

The calculation of dN/dS:

https://link.springer.com/protocol/10.1007/978-1-4939-1438-8_4

计算和内涵详解：

https://zhuanlan.zhihu.com/p/626367634
https://bioinformatics.cvr.ac.uk/calculating-dnds-for-ngs-datasets/ ：原文，很重要