R：`plot.ts（）`的ylab中的希臘字母`

Question

plot.ts()提供了一種可視化多變量時間序列的簡便方法。不幸的是，我無法弄清楚如何用希臘字母標註（重複）水平軸。插入希臘字母熟悉的做法似乎沒有工作，也沒有我嘗試了一些不太聰明的辦法：

testdata = matrix(rnorm(300), ncol = 3) 
# doesn't work 
plot.ts(testdata, ylab = expression(paste(pi[0], " = 0"))) 
# doesn't work 
plot.ts(testdata, ylab = c(expression(paste(pi[0], " = 0")), 
          expression(paste(pi[0], " = 1")), 
          expression(paste(pi[0], " = 2")))) 
# doesn't work 
colnames(testdata) = c(expression(paste(pi[0], " = 0")), 
         expression(paste(pi[0], " = 1")), 
         expression(paste(pi[0], " = 2"))) 
plot.ts(testdata) 
# doesn't work 
plot.ts(testdata, ylab = parse(text = y)) 

我已經江郎才盡......

Answer 1

有使用library(zoo)解決方案

testdata = matrix(rnorm(300), ncol = 3) 
plot(zoo::as.zoo(testdata),ylab=c(expression(mu),expression(sigma),expression(beta)),main="Win!") 

適於從http://r.789695.n4.nabble.com/How-to-change-the-label-in-plot-ts-td796114.html