如何在ggplot2中标记geom_dotplot的点？

Question

说我有这个简单的dotplot：

ggplot(mtcars, aes(hp)) +
  geom_dotplot(binwidth = 10, stackdir = 'center')

我想标记（部分）这些要点。这不起作用：

ggplot(mtcars, aes(hp)) +
  geom_dotplot(binwidth = 10, stackdir = 'center') +
  geom_text(aes(label = rownames(mtcars)))
# Error: geom_text requires the following missing aesthetics: y

那么如何才能访问为y计算的geom_dotplot值，以便我可以将标签放在正确的位置？

如果我设置y = 0并使用geom_text_repel，我会：

ggplot(mtcars, aes(hp)) +
  geom_dotplot(binwidth = 10, stackdir = 'center') +
  geom_text_repel(aes(label = rownames(mtcars)), box.padding = unit(2, 'lines'), y = 0)

这与我想要的很接近，除了所有线段都指向y = 0。

修改

我使用已接受答案的修改来尝试从设备尺寸推断y缩放量：

library(ggplot2)
library(ggrepel)

bw <- 10

p <- ggplot(mtcars, aes(hp)) +
geom_dotplot(binwidth = bw, stackdir = 'center')

built <- ggplot_build(p)
point.pos <- built$data[[1]]

# Order rows of mtcars by hp
idx <- order(mtcars$hp)
mtcars2 <- mtcars[idx,]

# Get the dimensions of the target device in pixels
size <- dev.size(units = 'px')
# Get the range of x and y domain values
extent <- with(built$layout$panel_params[[1]], abs(c(diff(x.range), diff(y.range))))
mtcars2$ytext <- (size[1] / size[2]) * (extent[2] / extent[1]) * point.pos$stackpos * bw
mtcars2$xtext <- point.pos$x

ggplot(mtcars2, aes(hp)) +
geom_dotplot(binwidth = bw, stackdir = 'center') +
geom_text_repel(
    aes(xtext, ytext, label = rownames(mtcars2)),
    box.padding = unit(.5 * size[1] * bw / extent[1], 'points'),
    color = 'red'
)

哪个产生

它并不完美 - 细分不会指向点的确切中心，因为整个图像的纵横比与面板的纵横比不同，但它和＃39;非常接近。

Answer 1

下面提出的代码并不优雅 它在缩放因子library(ggplot2) p <- ggplot(mtcars, aes(hp)) + geom_dotplot(binwidth = 10, stackdir = 'center') # Get y-positions of points plotted by geom_dotplot # Warning: these positions are not given point.pos <- ggplot_build(p)$data[[1]] # Order rows of mtcars by hp idx <- order(mtcars$hp) mtcars2 <- mtcars[idx,] # scale.fact needs fine tuning # It is strictly connected to the dimensions of the plot scale.fact <- 0.105 mtcars2$ytext <- point.pos$stackpos*scale.fact mtcars2$xtext <- point.pos$x lbls <- gsub(" ","\n",rownames(mtcars2)) png(file="myplot.png", width=4000, height=1400, res=300) ggplot(mtcars2, aes(hp)) + geom_dotplot(binwidth = 10, stackdir = 'center', fill="#AAAAAA55") + geom_text(aes(label=lbls, x=xtext, y=ytext), size=2) dev.off() 和绘图尺寸的微调之后起作用 我希望我的答案中包含的一些想法可以用来解决你的问题。

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