R语言自定义坐标轴排序：https://www.jianshu.com/p/2c99b33de56b
R语言数据集合并、数据增减、不等长合并：https://blog.csdn.net/sinat_26917383/article/details/50676894
数据整理之取子集：https://gaolei786.github.io/r/quziji.html
Fisher’s exact test in R: independence test for a small sample：https://towardsdatascience.com/fishers-exact-test-in-r-independence-test-for-a-small-sample-56965db48e87
