r - 在 R 图的图例文本中使用子/上标和特殊字符

Question

我为多个数据集生成了一个图。每个数据集都应该有自己的图例，其中可能包含希腊字母、plotmath 符号或 sub 和 superscrition。我想循环生成图例文本。

如果只有一个图例文本，Bquote 工作正常。如果我尝试添加额外的图例文本， plotmath-commads 会丢失，...

x <- 0:10
y1 = x * x
y2 = x * 10

plot (1,1, type="n", xlab=bquote(Omega), ylab="Y", las=1, xlim=range(x), ylim=range(y1, y2))
lines(x, y1, col=1, pch=1, type="b")
lines(x, y2, col=2, pch=2, type="b")

# generate legend texts (in a loop)
legend_texts = c(
  bquote(Omega^2)
  , bquote(Omega%*%10)
)
# Using a single bquote works fine:
#legend_texts = bquote(Omega^2)
#legend_texts = bquote(Omega%*%10)

legend(
  "topleft"
  , legend = legend_texts
  , col = c(1:2)
  , pch = c(1:2)
  , lty = 1
  )

Answer 1

将“legend_texts”更改为:

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

来自 ?legend 的帮助页面，“传奇”参数被描述为:

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

输出: