如何在ggplot2中让y轴上的线条彼此靠近且贴近x轴

问题背景 #

使用给定数据集和ggplot代码绘制横向误差棒图时，需要实现两个需求：

• Y轴上的三个标签彼此更紧凑
• 标签整体贴近X轴

此前使用scale_y_discrete(labels = yaxis, expand = expansion(add = 2))的方案会增大标签与X轴的距离，不符合当前需求。

数据集 #

df <- structure(list(vec = c("PC", "DEFAULT", "INFORMED"), mean = c(1.34944359241928, 
                                                      1.36249329506777, 1.34671188869646), sd = c(0.57779881866326, 
                                                                                                  0.537279303541924, 1.53585580464849), min = c(0.196903771571785, 
                                                                                                                                                0.28781509871908, -1.66860228474139), `0.5quant` = c(1.35295469982876, 
                                                                                                                                                                                                     1.36643973099316, 1.34687516700723), max = c(2.48177705326348, 
                                                                                                                                                                                                                                                  2.41483607230639, 4.36109982194179), mode = c(NA_real_, NA_real_, 
                                                                                                                                                                                                                                                                                                NA_real_), kld = c(1.9807860333589e-08, 2.97333113261951e-08, 
                                                                                                                                                                                                                                                                                                                   3.91753938449056e-10), ID = 1:3), row.names = c(NA, -3L), class = "data.frame")

原绘图代码 #

yaxis <- c(
  "Ppppppppp ppppppp
pppp pp pppppp
(ppp)",
  "Uuuuuuuuu uuuuu","Iiiiiii iiiii
ii Iiiiii (iiii)") 

ggplot(data = df, aes(x = mean, y = factor(ID))) + geom_point() + geom_errorbarh(aes(xmin = min, xmax = max), height = .1) + geom_vline(xintercept = 0, linetype = 2) + scale_x_continuous(breaks = seq(-4, 4.5, 0.5)) + scale_y_discrete(labels = yaxis) + theme(axis.text.y = element_text(hjust = .5))

解决方案 #

通过调整scale_y_discrete的expand参数，同时可选微调误差棒高度，实现标签紧凑且贴近X轴的效果：

ggplot(data = df, aes(x = mean, y = factor(ID))) + 
  geom_point() + 
  # 可选：缩小误差棒高度增强紧凑感
  geom_errorbarh(aes(xmin = min, xmax = max), height = 0.05) + 
  geom_vline(xintercept = 0, linetype = 2) + 
  scale_x_continuous(breaks = seq(-4, 4.5, 0.5)) + 
  # 调整Y轴扩展空间：底部负值贴近X轴，顶部少量扩展避免标签截断
  scale_y_discrete(labels = yaxis, expand = expansion(add = c(-0.3, 0.1))) + 
  theme(axis.text.y = element_text(hjust = .5))

参数说明 #

• expand = expansion(add = c(-0.3, 0.1))：add参数的两个值分别对应Y轴底部（靠近X轴）和顶部的扩展空间。负值会减少底部空白，让标签更贴近X轴；顶部保留少量正值避免最上方标签被截断。
• height = 0.05：缩小误差棒的高度，让整体布局更紧凑，可根据需求调整数值。

如果需要进一步微调整体边距，可添加plot.margin参数：

+ theme(
    axis.text.y = element_text(hjust = .5),
    plot.margin = margin(t = 10, r = 10, b = 10, l = 10, unit = "pt")
  )

内容的提问来源于stack exchange，提问作者Rustam