在R中使用ggplot2创建两个变量的有向箭头图

一个小男孩

我在两个时间点（）(V1,V2)对同一主题（id）测量了两个变量timepoint。我想要一个带有箭头路径的散点图，以显示同一主题的值如何从T1移到T2。

在我的示例中，某些主题的inV1或in都没有变化，V2理想的情况是为这些子项显示一个点（例如sub 1），但是我可以在两次访问中显示两个点，因为它们会重叠。V1或减少的V2子项（例如，子项2），这些子项显示在上方的红色箭头中。第三组主题显示V1或V2 （子6和7）增加：这些子为绿色。

但是，我真正需要的是所有箭头从T1指向T2。那就是我希望绿色箭头改变方向。

可以通过以下方式生成数据集：

datatest <- data.frame(timepoint =rep(seq(2,1),8), 
                   id = c(1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8),
                   V1= c( 30.29, 30.29, 21.60, 31.43, 20.75,20.75, 21.60, 30.03, 21.60, 31.30, 31.60, 21.72, 31.6, 20.02, 11.60, 20.16),
                   V2=c(40, 40, 30.78, 41.63, 40.41, 40.41,30.78, 40.97, 20.78, 40.84, 41.85, 41.85, 40.78, 31.79,20.78, 30.23))

看起来像这样：

   timepoint id    V1    V2
1          2  1 30.29 40.00
2          1  1 30.29 40.00
3          2  2 21.60 30.78
4          1  2 31.43 41.63
5          2  3 20.75 40.41
6          1  3 20.75 40.41
7          2  4 21.60 30.78
8          1  4 30.03 40.97
9          2  5 21.60 20.78
10         1  5 31.30 40.84
11         2  6 31.60 41.85
12         1  6 21.72 41.85
13         2  7 31.60 40.78
14         1  7 20.02 31.79
15         2  8 11.60 20.78
16         1  8 20.16 30.23

要生成我当前拥有的（错误的）图，请运行以下代码：

library(ggplot2)
library(lemon)
ggplot(datatest, aes(V1,V2,color=as.factor(timepoint),group=id)) +ggtitle("V2 vs V1 from T1 to T2")+
  geom_pointline(linesize=1, size=2, distance=4, arrow = arrow(angle = 30, length = unit(0.1, "inches"), ends = "first", type = "open") )+
  scale_x_continuous(limits = c(0,33), breaks=seq(0,30,10), expand = c(0, 0)) +
  scale_y_continuous(limits = c(0,43), breaks=seq(0,44,10),expand = c(0, 0))+
  scale_color_manual(values=c("green","red"))+labs(color  = "Timepoint")

该图当前如下所示：

谢谢！

保罗·范·奥本

这会让您更近吗？

library(dplyr)
library(tidyr)
library(ggplot2)


data <- data.frame(timepoint =rep(seq(2,1),8), 
                       id = c(1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8),
                       V1= c( 30.29, 30.29, 21.60, 31.43, 20.75,20.75, 21.60, 30.03, 21.60, 31.30, 31.60, 21.72, 31.6, 20.02, 11.60, 20.16),
                       V2=c(40, 40, 30.78, 41.63, 40.41, 40.41,30.78, 40.97, 20.78, 40.84, 41.85, 41.85, 40.78, 31.79,20.78, 30.23))


data <- data %>%
  mutate(row_id = paste0("T", timepoint)) %>%
  pivot_wider(id_cols = id,
              names_from = row_id,
              values_from = c(V1, V2)) %>%
  mutate(colour = ifelse((V1_T1 > V1_T2) | (V2_T1 > V2_T2), "red", "green"))

ggplot(data = data) +
  geom_point(aes(x = V1_T1, y = V2_T1)) +
  geom_point(aes(x = V1_T2, y = V2_T2)) +
  geom_segment(aes(x = V1_T1, xend = V1_T2, y = V2_T1 , yend = V2_T2, colour = colour),
               arrow = arrow(length = unit(0.3,"cm"))) +
  scale_x_continuous(
    limits = c(0, 33),
    breaks = seq(0, 30, 10),
    expand = c(0, 0)
  ) +
  scale_y_continuous(
    limits = c(0, 43),
    breaks = seq(0, 44, 10),
    expand = c(0, 0)
  )

您可以过滤对象data以删除那些V1和V2不变且不绘制长度为零的线的线。