使用带对象的多线表达式注释ggplot图？

I would like to make an annotation on my ggplot with two lines, sub- and superscripts, and references to objects.

我想在我的ggplot上做一个注释，包括两行，子和上标，以及对象的引用。

I've figured out that the annotate() function calls geom_text() which when parse = TRUE can use expressions from plotmath.

我已经发现annotate（）函数调用geom_text（），当parse = TRUE时，它可以使用plotmath中的表达式。

If this is my label:

如果这是我的标签：

q10 = 1.9
a = 3.9
b = -0.05

lab1 = substitute(atop(paste(Q[10], '=', q10), paste(M[O[2]], '=', a, e^(b*T))), list(q10 = q10 = 1.9, a = 3.9, b = -0.05))

Then it will work with base plot:

然后它将与基础图一起使用：

plot(1, 1, main = lab1)

But when I try to use it with ggplot() it throws an error:

但是当我尝试将它与ggplot（）一起使用时，它会抛出一个错误：

ggplot(diamonds, aes(carat, price, color = cut)) + 
  geom_point() +
  annotate(geom = 'text', x = 4, y = 5000, label = lab1, parse = TRUE, color = 'blue')

Error: Aesthetics must be either length 1 or the same as the data (1): label, colour

错误：美学必须是长度1或与数据（1）相同：标签，颜色

I found questions related to multi-line annotations in ggplot: R ggplot annotated with atop using three values and bgoup

我在ggplot中找到了与多行注释相关的问题：使用三个值和bgoup用atop注释的R ggplot

and related to expressions in ggplot: ggplot2 annotation with superscripts

并与ggplot中的表达式相关：带上标的ggplot2注释

But I can't figure out how to combine the appropriate answers to make a working annotation. Any help from the ggplot2 gurus out there?

但我无法弄清楚如何结合适当的答案来制作工作注释。那里有ggplot2专家的帮助吗？

1 个解决方案

#1

To use plotmath with ggplot, you pass it in as a string—parse = TRUE refers to parsing the string. Thus:

要将plotmath与ggplot一起使用，请将其作为string-parse = TRUE传递给它来解析字符串。从而：

library(ggplot2)

ggplot(diamonds, aes(carat, price, color = cut)) + 
    geom_point() +
    annotate(geom = 'text', x = 4, y = 5000, 
             label = "atop(Q[10] == 1.9,M[O[2]] == 3.9*e^(-0.05*T))", 
             parse = TRUE, color = 'blue')

If you need to substitute into the string, either use paste or glue::glue.

如果你需要替换成字符串，可以使用paste或glue :: glue。