如何在R的ggplot中调整Y轴间距，凸显低值氮曲线动态？

我绘制了多种氮类型的曲线图，其中两种在水体中的检测浓度远低于另一种。我希望观察红线与蓝线之间的动态变化，但由于绿线数值过高，Y轴被过度拉伸，导致0-0.5区间的规律难以看清。需要调整Y轴区间，展示0-0.5区间内的变化规律，类似实现Y轴断裂（Y-break）的效果。

sampleSites <- list("BVR1", "BVR2", "BVR3", "BVR4","BVR5", "BVR6")

samplePlotList <- list()


for (site in sampleSites){
  dat <- subset(nitrogen, ID==site)
  samplePlotList[[site]] <-
    dat %>%
    ggplot(aes_string(x="Month", y="value", group="condition")) +
    geom_line(size=0.5, aes(colour=condition)) +
    theme_classic() +
    theme(legend.position='none') +
    theme(text=element_text(size=10, family='Calibri')) +
    theme(axis.text=element_text(size=10, family='Calibri')) +
    labs(x= NULL) +
    ylim(0, 9) +
    theme(plot.margin = margin(0.75,0,0.5,0, "cm"))
}

structure(list(ID = structure(1:6, levels = c("BVR1", "BVR2", 
"BVR3", "BVR4", "BVR5", "BVR6"), class = "factor"), Survey = c(1L, 
1L, 1L, 1L, 1L, 1L), Month = structure(c(1L, 1L, 1L, 1L, 1L, 
1L), levels = c("Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", 
"Aug", "Sep", "Oct", "Nov", "Dec"), class = "factor"), Date = c("24/01/2022", 
"24/01/2022", "24/01/2022", "24/01/2022", "24/01/2022", "24/01/2022"
), Total.Nitrogen = c(4.987497648, 4.901992077, 3.837696783, 
4.389720566, 3.853376279, 1.696494226), DO = c(9, 9.4, 8.3, 8.5, 
8.8, 8.7), condition = c("Ammonia", "Ammonia", "Ammonia", "Ammonia", 
"Ammonia", "Ammonia"), value = c(0.063, 0.066888889, 0.065333333, 
0.035, 0.052888889, 0.035)), row.names = c(NA, 6L), class = "data.frame")

可以使用ggbreak包实现Y轴断裂，既聚焦0-0.5区间的细节，又保留高值数据的展示：

方法1：Y轴断裂展示全量数据 #

1. 安装并加载ggbreak包：

install.packages("ggbreak")
library(ggbreak)

2. 修改原有代码，替换ylim(0,9)为scale_y_break配置断裂规则：

sampleSites <- list("BVR1", "BVR2", "BVR3", "BVR4","BVR5", "BVR6")

samplePlotList <- list()


for (site in sampleSites){
  dat <- subset(nitrogen, ID==site)
  samplePlotList[[site]] <-
    dat %>%
    ggplot(aes_string(x="Month", y="value", group="condition")) +
    geom_line(size=0.5, aes(colour=condition)) +
    theme_classic() +
    theme(legend.position='none') +
    theme(text=element_text(size=10, family='Calibri')) +
    theme(axis.text=element_text(size=10, family='Calibri')) +
    labs(x= NULL) +
    # 设置Y轴在0.5-8区间断裂，前后刻度比例分别为1（0-0.5区间）和0.2（8-9区间）
    scale_y_break(c(0.5, 8), scales = c(1, 0.2)) +
    ylim(0, 9) +
    theme(plot.margin = margin(0.75,0,0.5,0, "cm"))
}

代码说明 #

• scale_y_break(c(0.5, 8))：指定Y轴跳过0.5到8的区间，避免该区间拉伸低数值部分的显示比例。
• scales = c(1, 0.2)：让0-0.5区间的刻度更密集，方便观察低浓度氮类型的变化规律；高值区间刻度稀疏，仅保留数据存在的范围。

方法2：仅聚焦0-0.5区间 #

如果不需要展示高值数据的细节，可直接限制Y轴范围为0-0.5，最大化低浓度曲线的展示空间：

sampleSites <- list("BVR1", "BVR2", "BVR3", "BVR4","BVR5", "BVR6")

samplePlotList <- list()


for (site in sampleSites){
  dat <- subset(nitrogen, ID==site)
  samplePlotList[[site]] <-
    dat %>%
    ggplot(aes_string(x="Month", y="value", group="condition")) +
    geom_line(size=0.5, aes(colour=condition)) +
    theme_classic() +
    theme(legend.position='none') +
    theme(text=element_text(size=10, family='Calibri')) +
    theme(axis.text=element_text(size=10, family='Calibri')) +
    labs(x= NULL) +
    ylim(0, 0.5) +
    theme(plot.margin = margin(0.75,0,0.5,0, "cm"))
}

这种方式简洁直观，适合重点关注低浓度氮类型动态变化的场景，高值数据可单独绘制汇总图表补充展示。

内容的提问来源于stack exchange，提问作者Melanie Baker