将"legend_texts"更改为:

Change "legend_texts" to:

# generate legend texts (in a loop)
legend_texts = c(
  as.expression(bquote(Omega^2))
  , as.expression(bquote(Omega%*%10))
)

在?legend的帮助页面中，传奇"参数描述为:

From the help page for ?legend, the "legend" argument is described as:

字符或表达载体.长度≥1的字符出现在图例中.其他对象将由as.graphicsAnnot强制.

a character or expression vector. of length ≥ 1 to appear in the legend. Other objects will be coerced by as.graphicsAnnot.

输出: