添加带有 x 条和舍入值的 geom_text

Question

我有一个 6 面 ggplot2 条形图。我希望每个方面都用其各自的平均值进行注释。像这样：

x̄ = 0.25

所以我一直在努力：

geom_text (data = averages, inherit.aes = FALSE,
           aes (label = expression (bar (x) == round (Mean, 2)), x = 30, y = 61.5)) +

但我总是得到这样的回报：

Don't know how to automatically pick scale for object of type <expression>. Defaulting to continuous.
Error in `geom_text()`:
! Problem while computing aesthetics.
ℹ Error occurred in the 2nd layer.
Caused by error in `compute_aesthetics()`:
! Aesthetics are not valid data columns.
✖ The following aesthetics are invalid:
✖ `label = expression(bar(x) == round(Mean, 2))`
ℹ Did you mistype the name of a data column or forget to add `after_stat()`?
Run `rlang::last_trace()` to see where the error occurred.

我还尝试了这两篇文章中的大多数建议：在绘图标签中组合粘贴（）和表达式（）函数和将数学符号和下标与常规字母混合

有什么办法可以做到这一点吗？

Answer 1

一种选择是将

paste(0)

与

parse=TRUE

一起使用，如下所示：

averages <- data.frame(
  facet = letters[1:6],
  Mean = 1:6
)

library(ggplot2)

ggplot() +
  geom_text(
    data = averages, inherit.aes = FALSE,
    aes(label = paste0("bar(x) == ", round(Mean, 2)), x = 30, y = 61.5),
    parse = TRUE
  ) +
  facet_wrap(~facet)

Answer 2

您可以使用

bquote

代替

expression

，并确保转义

.()

内的任何计算。注释最好使用

annotate

而不是

geom_text

添加

library(ggplot2)

Mean <- mean(iris$Sepal.Length)

ggplot(iris) +
  geom_point(aes(Sepal.Width, Sepal.Length, color = Species)) +
  annotate('text', x = 3.25, y = 8,
           label = bquote(bar (x) == .(round(Mean, 2))))