使用patchwork组合ggplot图时y轴标签对齐问题求助

我用ggplot创建了三个独立绘图，随后使用patchwork将它们垂直组合在一起。第三个绘图借助facet_grid添加了显示年份的次级x轴，但这导致它的y轴标签与绘图紧密相连，没有像前两个图那样留有间隔。尝试调整margin、vjust/hjust都未能解决问题，请问有什么方法可以对齐y轴标签？

我的代码： #

#First graph
presence <- ggplot(df_long, aes(x = date)) +
 geom_bar(aes(y = total_presence, fill = "Presence"), stat = "identity", width = 1, position = "stack") +
 geom_bar(aes(y = total_song, fill = "Song"), stat = "identity", width = 1, position = "stack") +
 geom_bar(data = filter(df_long, is.na(total_presence) & is.na(total_song)),
 aes(x=date, y =24), fill = "azure3", stat="identity", width = 1, position = "stack") +
 scale_fill_manual(values = c("Presence" = "olivedrab", "Song" = "olivedrab3"), name = "Detections") +
 scale_y_continuous(name = "Presence", breaks = seq(0,24,by=2), limits = c(0,24),expand=c(0,0))+
 scale_x_date(date_labels = "%b", date_breaks="1 month", expand= c(0,0))+
 labs(x=NULL, y = "Total Detections", title = paste(location)) +
 theme_minimal() +
 theme(axis.title.y = element_text(color = "black"),
 axis.text.y = element_text(color = "black"),
 axis.ticks.y=element_line(color="black"),
 panel.grid = element_blank(),
 legend.position = "right",
 plot.title = element_text(hjust = 0.5))
 
#Second graph
ice_temp <- ggplot(df_long, aes(x=date)) +
 geom_bar(aes(y=Proportion,fill=Ice_Type), stat = "identity", position = "stack", width = 1) +
 geom_line(aes(y = (sst_mean/4)+0.5), color = "red", size = 0.4) +
 labs(x=NULL, y="Sea Ice Proportion", title = NULL)+
 scale_fill_manual(values = c(
         "VeryOpenDriftIce" = "#7FDBFF",
         "OpenDriftIce" = "#0074D9",
         "CloseDriftIce" = "#00457e",
         "VeryCloseDriftIce" = "#001f3f",
         "FastIce" = "red"
       )) +
 theme_minimal() +
 scale_y_continuous(limits=c(0, NA), expand=c(0,0),
 sec.axis = sec_axis(~ (.-0.5)*4, name = "Sea Surface Temperature (°C)",
 breaks = seq(-2,2,by=1)))+
 scale_x_date(date_labels = "%b", date_breaks="1 month", expand= c(0,0))+
 theme(panel.grid = element_blank(), legend.position = "right",
 axis.ticks = element_line(),
 axis.title.y.right = element_text(color = "red"),
 axis.text.y.right = element_text(color = "red"),
 axis.ticks.y.right=element_line(color="red"))
  
 #third graph
zooc_chl <- ggplot(df_long, aes(x=date)) +
 geom_line(aes(y=zooc_mean),color="#D55E00", size = 0.4) +
 geom_line(aes(y=chl_mean),color="#0072B2",size=0.4)+
 labs(x=NULL, y="<span style = 'color:#D55E00;'>Zooplankton [g/m<sup>2</sup>]</span>  
<span style = 'color:#0072B2;'>Chlorophyll a [mg/m<sup>3</sup>]</span>", title = NULL)+
 scale_y_continuous(breaks = seq(0,3,by=0.5), limits = c(0,3),expand=c(0,0))+
 scale_x_date(date_labels = "%b", date_breaks="1 month", expand= c(0,0))+
 facet_grid(~ year(date), space= "free", scales="free",switch="x") +
 theme_minimal() +
 theme(axis.title.y=element_markdown(),
 strip.placement = "outside",
 axis.ticks = element_line(),
 strip.background = element_rect(fill=NA,colour="grey50"),
 panel.spacing=unit(0,"cm"))
 
 #combine graphs
combined_plot <- presence / ice_temp / zooc_chl

问题效果： #

解决方案 #

问题根源是facet_grid的switch="x"将年份strip移到x轴外侧，改变了绘图区域的边距计算逻辑，压缩了y轴标签的可用空间。以下三种方法都能解决：

方法1：统一设置所有图的左边距 #

给三个图的theme添加相同的左边距，确保y轴标签有足够的显示空间。数值可以根据标签长度调整：

修改第三个图的theme：

theme_minimal() +
theme(axis.title.y=element_markdown(),
      strip.placement = "outside",
      axis.ticks = element_line(),
      strip.background = element_rect(fill=NA,colour="grey50"),
      panel.spacing=unit(0,"cm"),
      plot.margin = margin(t=5, r=5, b=5, l=20, unit="pt")) # 统一左边距

前两个图也需要添加同样的plot.margin参数，确保三个图的左侧边距完全一致。

方法2：用patchwork全局统一边距 #

无需逐个修改图，在拼接时通过plot_layout配合全局theme设置统一边距：

combined_plot <- presence / ice_temp / zooc_chl +
  plot_layout(guides = "collect") + # 可选：合并图例，优化布局
  theme(plot.margin = margin(t=5, r=5, b=5, l=20, unit="pt"))

方法3：单独调整facet图的y轴标题边距 #

针对第三个图，直接给y轴标题添加右侧边距，让它和绘图区域拉开距离，匹配前两个图的标签位置：

theme_minimal() +
theme(axis.title.y=element_markdown(margin = margin(r=10, unit="pt")), # 给y轴标题加右侧间隔
      strip.placement = "outside",
      axis.ticks = element_line(),
      strip.background = element_rect(fill=NA,colour="grey50"),
      panel.spacing=unit(0,"cm"))

调整后重新拼接，三个图的y轴标签即可对齐。

内容的提问来源于stack exchange，提问作者Lucat