如何在Tukey的测试中添加字母？我可以执行Tukey，但不分配字母。 这是我的代码
SOC = c(162.02, 127.41, 146.99, 133.2, 110.99, 107.29, 103.8, 96.99, 141.24, 108.19, 120.35, 92.52, 122.56, 79.19, 76.38, 79.17, 188.78 , 176.28, 164.33, 154.03)
Treatments = c(rep("CG",4), rep("CM",4), rep("TG",4),rep("HG",4), rep("FO",4))
Wholesoil = data.frame(SOC,Treatments)
results = aov(SOC ~ Treatments, data=Wholesoil)
summary(results)
TukeyHSD(results, conf.level = 0.95)
plot(results)