如何在R中为两个相关矩阵的geom_tile添加箭头？

当然可以自动生成你需要的箭头，下面提供两种基于R的实现方案，直接复用你原有的代码逻辑：

方案一：基于grid包手动定位箭头 #

这种方法通过grid系统的viewport精准控制绘图位置，适合需要精细调整箭头位置的场景：

library(gridExtra)
library(ggplot2)
library(grid)
library(purrr)
library(reshape2) # 补充melt函数依赖包

# 生成模拟数据
X <- data.frame("x1" = rnorm(100, 0, 1),
                "x2" = rnorm(100, 0, 1),
                "x3" = rnorm(100, 0, 1))

# 定义热力图绘制函数
plotCors <- function(df)
{
  ggplot(df, 
         aes(x = X1, 
             y = X2, fill = value)) +
    geom_tile() +
    labs(x = "", y = "") # 移除轴标签，让布局更紧凑
}

# 生成两个相关矩阵的melt数据，第二个矩阵交换x2和x3的顺序
cor1 <- melt(cor(X))
cor2 <- melt(cor(X))
cor2$X1 <- factor(cor2$X1, levels = c("x1", "x3", "x2"))
cor2$X2 <- factor(cor2$X2, levels = c("x1", "x3", "x2"))

plots_list <- map(list(cor1, cor2), plotCors)

# 创建新的绘图页面
grid.newpage()

# 设置两个图的布局视口，中间预留箭头空间
vp_left <- viewport(x = 0.225, y = 0.5, width = 0.45, height = 1)
vp_right <- viewport(x = 0.775, y = 0.5, width = 0.45, height = 1)

# 绘制左右两个热力图
print(plots_list[[1]], vp = vp_left)
print(plots_list[[2]], vp = vp_right)

# 绘制第一个箭头：左图x2单元格 → 右图x3单元格
grid.segments(x0 = 0.45, y0 = 0.5, x1 = 0.55, y1 = 0.5,
              arrow = arrow(type = "open", length = unit(0.1, "inches")),
              gp = gpar(lwd = 1.5))

# 绘制第二个箭头：左图x3单元格 → 右图x2单元格
grid.segments(x0 = 0.45, y0 = 0.167, x1 = 0.55, y1 = 0.167,
              arrow = arrow(type = "open", length = unit(0.1, "inches")),
              gp = gpar(lwd = 1.5))

方案二：基于patchwork包快速布局（更简洁） #

patchwork包简化了多图布局，适合快速实现需求：

library(patchwork)
library(ggplot2)
library(reshape2)
library(grid)

# 模拟数据和绘图函数同方案一
X <- data.frame("x1" = rnorm(100, 0, 1),
                "x2" = rnorm(100, 0, 1),
                "x3" = rnorm(100, 0, 1))

plotCors <- function(df)
{
  ggplot(df, 
         aes(x = X1, 
             y = X2, fill = value)) +
    geom_tile() +
    labs(x = "", y = "")
}

cor1 <- melt(cor(X))
cor2 <- melt(cor(X))
cor2$X1 <- factor(cor2$X1, levels = c("x1", "x3", "x2"))
cor2$X2 <- factor(cor2$X2, levels = c("x1", "x3", "x2"))

p1 <- plotCors(cor1)
p2 <- plotCors(cor2)

# 布局两个图，中间留空放置箭头
p <- p1 + plot_spacer(width = 0.2) + p2 + plot_layout(widths = c(4,1,4))

# 绘制箭头
print(p)
grid.segments(x0 = 0.42, y0 = 0.5, x1 = 0.58, y1 = 0.5,
              arrow = arrow(type = "open", length = unit(0.1, "inches")),
              gp = gpar(lwd = 1.5))
grid.segments(x0 = 0.42, y0 = 0.167, x1 = 0.58, y1 = 0.167,
              arrow = arrow(type = "open", length = unit(0.1, "inches")),
              gp = gpar(lwd = 1.5))

说明 #

• 两个方案都能自动生成你需要的箭头，箭头位置可以通过调整grid.segments的x/y坐标进行微调
• 方案一的视口定位更灵活，适合复杂布局；方案二的patchwork代码更简洁，上手更快

内容的提问来源于stack exchange，提问作者thesecond