如何在冲积/桑基图的flows项上添加值标签(在R ggalluvia图上)？

Question

我希望在R上标注冲积层/桑基图的“流”部分。

可以很容易地标记层(柱)，但不能标记连接它们的流。我所有的阅读文档和实验的尝试都是徒劳的。

在下面的示例中，"freq“应标记在流量连接部件上。

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library(ggplot2)
library(ggalluvial)

data(vaccinations)
levels(vaccinations$response) <- rev(levels(vaccinations$response))
ggplot(vaccinations,
       aes(x = survey, stratum = response, alluvium = subject,
           y = freq,
           fill = response, label = freq)) +
  scale_x_discrete(expand = c(.1, .1)) +
  geom_flow() +
  geom_stratum(alpha = .5) +
  geom_text(stat = "stratum", size = 3) +
  theme(legend.position = "bottom") +
  ggtitle("vaccination survey responses at three points in time")

Answer 1

有一个选项可以获取原始数字并将其用作流部分的标签：

ggplot(vaccinations,
       aes(x = survey, stratum = response, alluvium = subject,
           y = freq,
           fill = response, label = freq)) +
  scale_x_discrete(expand = c(.1, .1)) +
  geom_flow() +
  geom_stratum(alpha = .5) +
  geom_text(stat = "stratum", size = 3) +
  geom_text(stat = "flow", nudge_x = 0.2) +
  theme(legend.position = "bottom") +
  ggtitle("vaccination survey responses at three points in time")

​

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如果想要更多地控制如何标记这些点，可以提取图层数据并对其进行计算。例如，我们可以只计算起始位置的分数，如下所示：

# Assume 'g' is the previous plot object saved under a variable
newdat <- layer_data(g)
newdat <- newdat[newdat$side == "start", ]
split <- split(newdat, interaction(newdat$stratum, newdat$x))
split <- lapply(split, function(dat) {
  dat$label <- dat$label / sum(dat$label)
  dat
})
newdat <- do.call(rbind, split)

ggplot(vaccinations,
       aes(x = survey, stratum = response, alluvium = subject,
           y = freq,
           fill = response, label = freq)) +
  scale_x_discrete(expand = c(.1, .1)) +
  geom_flow() +
  geom_stratum(alpha = .5) +
  geom_text(stat = "stratum", size = 3) +
  geom_text(data = newdat, aes(x = xmin + 0.4, y = y, label = format(label, digits = 1)),
            inherit.aes = FALSE) +
  theme(legend.position = "bottom") +
  ggtitle("vaccination survey responses at three points in time")

​

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这仍然是一种判断，关于你到底想要把标签放在哪里。在开始时这样做是最简单的方法，但如果您希望这些标签大致位于中间并彼此闪避，则需要进行一些处理。