R ggplot：仅将标签应用于图中的最后 N 个数据点

Question

我在 R 中创建了一个折线图（绘图），每个数据点都带有标签。由于大量的数据点，绘图变得非常完整，带有标签。我只想为最后 N 个（比如 4 个）数据点应用标签。我在 geom_label_repel 函数中尝试了 subset 和 tail 但无法计算他们我们或收到错误消息。我的数据集包含 99 个值，分布在 3 个组 (KPI)。

我在 R 中有以下代码：

library(ggplot)
library(ggrepel)

data.trend <- read.csv(file=....)

plot.line <- ggplot(data=data.trend, aes(x = Version, y = Value, group = KPI, color = KPI)) +

  geom_line(aes(group = KPI), size = 1) +
  geom_point(size = 2.5) +


  # Labels defined here
  geom_label_repel(
    aes(Version, Value, fill = factor(KPI), label = sprintf('%0.1f%%', Value)),
    box.padding = unit(0.35, "lines"),
    point.padding = unit(0.4, "lines"),
    segment.color = 'grey50',
    show.legend = FALSE
  )

);

平心而论，我是 R 的新手。也许我错过了一些基本的东西。

提前致谢。

Answer 1

最简单的方法 是在 geom_label_repel 中设置 data = 参数以仅包括您要标记的点。

这是一个可重现的例子：

set.seed(1235)
data.trend <- data.frame(Version = rnorm(25), Value = rnorm(25), 
                         group = sample(1:2,25,T), 
                         KPI = sample(1:2,25,T))

ggplot(data=data.trend, aes(x = Version, y = Value, group = KPI, color = KPI)) +
  geom_line(aes(group = KPI), size = 1) +
  geom_point(size = 2.5) +
  geom_label_repel(aes(Version, Value, fill = factor(KPI), label = sprintf('%0.1f%%', Value)),
    data = tail(data.trend, 4),                 
    box.padding = unit(0.35, "lines"),
    point.padding = unit(0.4, "lines"),
    segment.color = 'grey50',
    show.legend = FALSE)

不幸的是，这与排斥算法有点混乱，使得标签放置相对于其他未标记的点不是最优的（你可以在上图中看到一些点被标签覆盖）。

因此，更好的方法 是使用 color 和 fill 来简单地使不需要的标签不可见（通过将颜色和填充都设置为 NA 对于要隐藏的标签):

ggplot(data=data.trend, aes(x = Version, y = Value, group = KPI, color = KPI)) +
  geom_line(aes(group = KPI), size = 1) +
  geom_point(size = 2.5) +
  geom_label_repel(aes(Version, Value, fill = factor(KPI), label = sprintf('%0.1f%%', Value)),
                   box.padding = unit(0.35, "lines"),
                   point.padding = unit(0.4, "lines"),
                   show.legend = FALSE,
                   color = c(rep(NA,21), rep('grey50',4)),
                   fill = c(rep(NA,21), rep('lightblue',4)))

Answer 2

如果您只想显示最后一个标签，使用 group_by 和过滤器可能有效：

data = data.trend %>% group_by(KPI) %>% filter(Version == max(Version))

完整示例：

suppressPackageStartupMessages(library(dplyr))
library(ggplot2)
library(ggrepel)

set.seed(1235)
data.trend <- data.frame(Version = rnorm(25), Value = rnorm(25), 
                         group = sample(1:2,25,T), 
                         KPI = sample(1:2,25,T))

ggplot(data = data.trend, aes(x = Version, y = Value, group = KPI, color = KPI)) +
  geom_line(aes(group = KPI), size = 1) +
  geom_point(size = 2.5) +

  # Labels defined here
  geom_label_repel(
    data = data.trend %>% group_by(KPI) %>% filter(Version == max(Version)), 
    aes(Version, Value, fill = factor(KPI), label = sprintf('%0.1f%%', Value)),
    color = "black",
    fill = "white")

或者如果您想为每个 KPI 显示 4 个随机标签，data.trend %>% group_by(KPI) %>% sample_n(4):

suppressPackageStartupMessages(library(dplyr))
library(ggplot2)
library(ggrepel)

set.seed(1235)
data.trend <- data.frame(Version = rnorm(25), Value = rnorm(25), 
                         group = sample(1:2,25,T), 
                         KPI = as.factor(sample(1:2,25,T)))

ggplot(data = data.trend, aes(x = Version, y = Value, group = KPI, color = KPI)) +
  geom_line(aes(group = KPI), size = 1) +
  geom_point(size = 2.5) +
  
  # Labels defined here
  geom_label_repel(
    data = data.trend %>% group_by(KPI) %>% sample_n(4), 
    aes(Version, Value, fill = factor(KPI), label = sprintf('%0.1f%%', Value), fill = KPI),
    color = "black", show.legend = FALSE
    )
#> Warning: Duplicated aesthetics after name standardisation: fill

^{由 reprex package (v2.0.1)}

于 2021-08-27 创建

R ggplot：仅将标签应用于图中的最后 N 个数据点

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