使用 facet_wrap 和 geom_segment 删除不必要的 y 轴点

Question

我使用geom_segment() 将y 轴点映射到x 轴，然后使用facet_wrap 将数据分成两个图；但是，两个图上都显示了 y 轴点。

我怎样才能只有与每个 facet_wrap 相关的必要 y 轴点？

示例代码

dat <- structure(list(temp = c(1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 
4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5), rev = c(-5, 
-11, -20, -29, -40, -9, -20, -32, -45, -57, -12, -24, -37, -50, 
-62, -7, -20, -36, -52, -67, -5, -13, -23, -35, -47, -12, -24, 
-36, -48, -58), type = c("Type 1", "Type 1", "Type 1", "Type 1", 
"Type 1", "Type 1", "Type 1", "Type 1", "Type 1", "Type 1", "Type 1", 
"Type 1", "Type 1", "Type 1", "Type 1", "Type 2", "Type 2", "Type 2", 
"Type 2", "Type 2", "Type 2", "Type 2", "Type 2", "Type 2", "Type 2", 
"Type 2", "Type 2", "Type 2", "Type 2", "Type 2"), model = c("A", 
"A", "A", "A", "A", "B", "B", "B", "B", "B", "C", "C", "C", "C", 
"C", "A", "A", "A", "A", "A", "B", "B", "B", "B", "B", "C", "C", 
"C", "C", "C")), .Names = c("temp", "rev", "type", "model"), row.names = c(NA, 
-30L), class = "data.frame")

p1 <- ggplot(dat, aes(temp, rev, color = model)) + 
  geom_line() + geom_point() + geom_segment(aes(x = 0, xend = temp, yend = rev), linetype = "dashed", color = "grey") + 
  facet_wrap(~type, scales = "free") + scale_y_continuous(breaks = dat$rev)
p1

情节

Answer 1

我编造了虚拟数据，因为出于某种原因将您的 dput 粘贴到我的控制台中会让人不高兴。

library(dplyr)

df <- expand.grid(temp = 1:5, model = LETTERS[1:3], type = 1:2) %>% 
  group_by(model, type) %>% 
  mutate(rev = -sort(sample.int(20, length(temp)))) 

# this is equivalent to your data as-is, structurewise

---

df.labeled <- df %>% 
  ungroup() %>% group_by(type, rev) %>% 
  mutate(label = c(rev[1], rep(NA, length(rev) - 1)))

在这里，我为每个组面板中显示的每个 y 值创建了一个组。然后我创建一个label 列，其中包含对该y 值的1 个观察值，并用NAs 填充。因此，如果一个面板有两个模型，每个模型都有一个 rev 或 -5，那么现在它将是 -5, NA 而不是 -5, -5。为什么我这样做会在下面变得更清楚。

---

ggplot(df.labeled, aes(temp, rev, color = model)) + 
  geom_segment(aes(xend = 0, yend = rev), linetype = "dashed", color = "grey") +
  geom_text(aes(label = label, x = -0.1), colour = "black", hjust = 1) +
  geom_vline(xintercept = 0) +
  geom_point() + geom_line() + facet_grid(~type) + 
  scale_y_continuous(breaks = NULL) + 
  scale_x_continuous(limits = c(-0.5, NA)) +
  theme_bw() + theme(panel.grid = element_blank())

如果我留下了重复项（此处为 -7，类型 1 为 -15，类型 2 为 -11），geom_text 将是一个凌乱的粗体模糊。重复的文本标签在 ggplot2 中呈现不佳。由于实际上不可能按照您想要的方式进行操作，因此我们只是为每个面板制作了一个假秤。如果您不喜欢数字左侧的 y 轴上有一条额外的线，可以去掉：

  ... + 
  theme(panel.grid = element_blank(),
        panel.border = element_blank(),
        axis.line.x = element_line())

Answer 2

我们可以通过type分割数据框，创建分离图，然后使用gridExtra包中的grid.arrange组合两个图。

library(ggplot2)
library(gridExtra)

# Split the data
dat_list <- split(dat, dat$type)

# Use lapply to create plot for both subset
p_list <- lapply(dat_list, function(x){

  p1 <- ggplot(x, aes(temp, rev, color = model)) + 
    geom_line() + 
    geom_point() + 
    geom_segment(aes(x = 0, xend = temp, yend = rev), linetype = "dashed", color = "grey") + 
    scale_y_continuous(breaks = x$rev) +
    facet_wrap(~type, scales = "free")
  return(p1)
})

# Plot the data
grid.arrange(grobs = p_list, nrow = 1)

更新

另一种选择是使用cowplot 包。这似乎是一种创造共同传奇的方式。

library(cowplot)

# Get the common legend, p_list is from the previous example
legend_both <- get_legend(p_list[[1]])

# Plot the plots and the common legend together
# Use rel_widths to set the column width
plot_grid(p_list[[1]] + theme(legend.position = "none"),
          p_list[[2]] + theme(legend.position = "none"),
          legend_both, 
          nrow = 1,
          rel_widths = c(2, 2, 1))