情节标题中的斜体希腊字母/乳胶式数学

问题描述

我想在 R 的情节标题中创建乳胶风格的数学.绘图数学工具 有一个有用但有限的表达式子集，它们可以显示，并使用非乳胶语法和样式.

I'd like to create latex-style math in plot titles in R. The plotmath tools have a useful but limited subset of expressions they can display, and use non-latex syntax and style.

例如，我想在图的标题中打印方程 $mathrm{d} mathbf{x} = a [heta - mathbf{x}] mathrm{d} t$，并且仍然评估某些变量的值.我最好的解决方案是非常麻烦:

For instance, I would like to print the equation $mathrm{d} mathbf{x} = a [heta - mathbf{x}] mathrm{d} t$ in the title of the plot, and still evaluate the value of certain variables. The best solution I have is the very cumbersome:

lambda <- 4
plot(1:10,1:10)

mtext(bquote(paste(d*bolditalic(x)[italic(t)] == alpha*(theta - bolditalic(x)[italic(t)] )*d*italic(t) +  .(lambda) * d * italic(B)[italic(t)] )), line=2.25,cex=2)

或

require(ggplot2)
qplot(1:10, 1:10) + opts(title=bquote(paste(d*bolditalic(x)[italic(t)] == alpha*(theta - bolditalic(x)[italic(t)] )*d*italic(t) +  .(lambda) * d * italic(B)[italic(t)] )), line=2.25,cex=2)

这个问题 几乎解决了这个问题，但是我失去了 bquote 显示的能力变量的数值(在我的示例中为 lambda).有没有办法将这些组合起来，以便我可以使用斜体希腊字母(变量的标准格式，例如由 tex 完成)并以特定值进行评估?

This question almost solves this, but I loose the ability of bquote to display the numerical value of a variable (lambda in my example). Is there a way to combine these so I can have italic greek letters (the standard format for variables, e.g. as done by tex) and evaluate at specific values?

有没有更好的方法可以让我简单地为方程编写 tex 语法并将它们添加到我的图表中?

Is there a much better way where I can simple write tex-syntax for equations and add them to my graphs?

推荐答案

您可能需要查看 tikzDevice 包(或查看 它的小插图优先)，它提供了一种在 R 图形中编写 LaTeX 数学的自然方式.

You may want to check out the tikzDevice package (or take a look at its vignette first), which provides a natural way to write LaTeX math in R graphics.

我也有这里有一个简单的例子.

这是另一个例子:

library(tikzDevice)
library(ggplot2)
tikz('math.tex', standAlone = TRUE, width = 4, height = 4)
qplot(1:10, 1:10,
  main = '$\mathrm{d} \mathbf{x} = a [\theta - \mathbf{x}] \mathrm{d} t$')
dev.off()

如果你运行 pdflatex math.tex 会产生这个:

which produces this if you run pdflatex math.tex:

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