ggalluvial：如何让区块间流线条顺序与数据框一致？

需求 #

使用ggalluvial绘制桑基图时，需要解决两个问题：

• 让黄色（Male）流线条始终位于紫色（Female）线条上方（覆盖x轴所有区块）
• 修复区块内文本位置错位的问题

已尝试排序数据框、指定因子层级、调整lode_order参数，但未达到预期效果。

可复现代码 #

原始数据创建代码 #

w <- c("Rain Forest", "Desert", "Arctic", "City", "Low Earth", "Boonies", "Space")
x <- 1:40
y <- c("Bird", "Tiger", "Cat", "Parrot", "T-Rex", "Dreadwing")

set.seed(0)
GenComp <- data.frame(
  Location = sample(w, size = 28, replace = TRUE),
  Frequency = sample(x = x, size = 28, replace = TRUE),
  Animal = sample(x = y, size = 28, replace = TRUE),
  Gender = rep(c("Male", "Female"), 14))

GenComp <- GenComp[order(GenComp$Gender, GenComp$Animal, GenComp$Location, decreasing = FALSE),]
row.names(GenComp) <- 1:nrow(GenComp)

GenComp$Location <- factor(GenComp$Location, levels = sort(unique(GenComp$Location)))
GenComp$Gender <- factor(GenComp$Gender, levels = c("Female", "Male"))
GenComp$Animal <- factor(GenComp$Animal, levels = sort(unique(GenComp$Animal)))
GenComp <- GenComp[, c(4, 3, 1, 2)]

原始绘图代码 #

library(ggalluvial)
ggplot(GenComp,aes(y = Frequency,
                            axis1 = Gender, axis2 = Animal, axis3 = Location)) + 
  geom_alluvium(aes(fill = Gender), width = 1/8, knot.pos = 0, reverse = FALSE) +
  geom_stratum(alpha = 0.25, width = 1/8, reverse = FALSE) +
  geom_text(stat = "stratum", aes(label = after_stat(stratum)), reverse = TRUE, size = 3)  +
  ggtitle("Distribution of Fauna") +
  scale_fill_manual(values = c(Female = "#691869", Male = "#EBBC55")) +
  guides(fill = "none") 

解决方法 #

关键调整思路 #

1. 统一流线条顺序：通过调整因子层级和排序规则，让Male相关的流线优先排列在上；同时在绘图层强制按Gender排序流向。
2. 修正文本位置：统一所有图层的reverse参数，让文本与区块的顺序完全匹配。

修改后的完整代码 #

# 创建数据框（调整排序与因子层级）
w <- c("Rain Forest", "Desert", "Arctic", "City", "Low Earth", "Boonies", "Space")
x <- 1:40
y <- c("Bird", "Tiger", "Cat", "Parrot", "T-Rex", "Dreadwing")

set.seed(0)
GenComp <- data.frame(
  Location = sample(w, size = 28, replace = TRUE),
  Frequency = sample(x = x, size = 28, replace = TRUE),
  Animal = sample(x = y, size = 28, replace = TRUE),
  Gender = rep(c("Male", "Female"), 14))

# 按Gender降序排序，确保Male相关行在前
GenComp <- GenComp[order(GenComp$Gender, GenComp$Animal, GenComp$Location, decreasing = TRUE),]
row.names(GenComp) <- 1:nrow(GenComp)

# 调整Gender因子层级，Male在前
GenComp$Location <- factor(GenComp$Location, levels = sort(unique(GenComp$Location)))
GenComp$Gender <- factor(GenComp$Gender, levels = c("Male", "Female"))
GenComp$Animal <- factor(GenComp$Animal, levels = sort(unique(GenComp$Animal)))
GenComp <- GenComp[, c(4, 3, 1, 2)]

# 绘图代码（修正参数）
library(ggalluvial)
ggplot(GenComp,aes(y = Frequency,
                   axis1 = Gender, axis2 = Animal, axis3 = Location)) + 
  # 添加order = Gender强制按性别排序流线
  geom_alluvium(aes(fill = Gender, order = Gender), width = 1/8, knot.pos = 0, reverse = TRUE) +
  geom_stratum(alpha = 0.25, width = 1/8, reverse = TRUE) +
  # 统一reverse参数，添加order绑定文本与区块顺序
  geom_text(stat = "stratum", aes(label = after_stat(stratum), order = after_stat(stratum)), 
            reverse = TRUE, size = 3)  +
  ggtitle("Distribution of Fauna") +
  scale_fill_manual(values = c(Male = "#EBBC55", Female = "#691869")) +
  guides(fill = "none") 

调整点说明 #

• 数据排序时设置decreasing = TRUE，配合Gender因子层级，让Male的记录排在数据集前面
• geom_alluvium中添加order = Gender，强制按性别因子层级排列流线，保证Male流线始终在上
• 统一所有图层的reverse参数为TRUE，避免流线、区块、文本的顺序错位
• 文本图层添加order = after_stat(stratum)，让文本位置与区块顺序完全对应，解决错位问题

内容的提问来源于stack exchange，提问作者Purrsia