用expression

比如
plot(rnorm(100), ylab = expression(X["bar"]), xlab = expression(Z^"0.05"))

1# statchao

我的程序如下：
par(mfrow = c(1,1))
xv<-seq(-4,4,0.01)
yv<-dnorm(xv)
plot(xv,yv,type="l",xlab=" ",ylab="")
polygon(c(xv[xv>=1.645],1.645),c(yv[xv>=1.645],yv[xv==4]),col="grey80", border = "red")
text(2.1+0.5, dnorm(1.645), "拒绝域", adj = c(0.5, 0), cex = 0.75)
arrows(2.6,0.09,2.6,0.015, angle = 10)
text(1.65, -0.015, "临界值1.645", adj = c(0.5, 0), cex = 0.75)
text(2.45, 0.005, "概率0.05", adj = c(0.5, 0), cex = 0.75)

text(0, 0.15, " 不拒绝expression(H['0'])，概率（或面积）为0.95", adj = c(0.5, 0), cex = 0.75)  
这里似乎不行，我需要弄出H_0来，还望指点一二！谢谢

text(3.6, 0.005, "z的范围", adj = c(0.5, 0), cex = 0.75)
abline(h=0)

我的复杂一些：
气体单位比如的上下标怎么打？一个单位里有3个上下标。我打出了一个上标，结果下不来了。后面的内容全成了上标了

你怎么解决的？

怎么这么麻烦，不是可以直接输入吗？