如何在ggplot2的geom_bar plot中設置雙Y軸？

Question

我想像這樣畫條 plot 但在雙 Y 軸上

( https://i.stack.imgur.com/ldMx0.jpg )

前三個索引的范圍是0到1，所以我希望左邊的y軸（對應NSE、KGE、VE）的范圍是0到1，右邊的y軸（對應PBIAS）的范圍是-15到 5。

以下是我的數據和代碼：

library("ggplot2")

## data
data <- data.frame(
  value=c(0.82,0.87,0.65,-3.39,0.75,0.82,0.63,1.14,0.85,0.87,0.67,-7.03),
  sd=c(0.003,0.047,0.006,4.8,0.003,0.028,0.006,4.77,0.004,0.057,0.014,4.85),
  index=c("NSE","KGE","VE","PBIAS","NSE","KGE","VE","PBIAS","NSE","KGE","VE","PBIAS"),
  period=c("all","all","all","all","calibration","calibration","calibration","calibration","validation","validation","validation","validation")
)

## fix index sequence
data$index <- factor(data$index, levels = c('NSE','KGE','VE',"PBIAS"))
data$period <- factor(data$period, levels = c('all','calibration', 'validation'))


## bar plot
ggplot(data, aes(x=index, y=value, fill=period))+ 
  geom_bar(position="dodge", stat="identity")+
  geom_errorbar(aes(ymin=value-sd, ymax=value+sd),
                position = position_dodge(0.9), width=0.2 ,alpha=0.5, size=1)+
  theme_bw()

我嘗試縮放和移動第二個 y 軸，但 PBIAS 條 plot 由於超出比例限制而被刪除，如下所示：

( https://i.stack.imgur.com/n6Jfm.jpg )

以下是我的雙 y 軸代碼：

## bar plot (scale and shift the second y-axis with slope/intercept in 20/-15)
ggplot(data, aes(x=index, y=value, fill=period))+ 
  geom_bar(position="dodge", stat="identity")+
  geom_errorbar(aes(ymin=value-sd, ymax=value+sd),
                position = position_dodge(0.9), width=0.2 ,alpha=0.5, size=1)+
  theme_bw()+
  scale_y_continuous(limits = c(0,1), name = "value", sec.axis = sec_axis(~ 20*.- 15, name="value")) 

對移動 bar_plot 或其他解決方案有什么建議嗎？

Answer 1

采用不同的方法，而不是使用雙軸，一種選擇是制作兩個單獨的圖並使用patchwork將它們粘合在一起。 恕我直言，這比擺弄重新縮放數據要容易得多（這是你錯過的步驟，即如果你想要一個輔助軸，你還必須重新縮放數據）並且更清楚地表明指數是在不同的尺度上測量的:

library(ggplot2)
library(patchwork)

data$facet <- data$index %in% "PBIAS"

plot_fun <- function(.data) {
  ggplot(.data, aes(x = index, y = value, fill = period)) +
    geom_bar(position = "dodge", stat = "identity") +
    geom_errorbar(aes(ymin = value - sd, ymax = value + sd),
                  position = position_dodge(0.9), width = 0.2, alpha = 0.5, size = 1
    ) +
    theme_bw()
}

p1 <- subset(data, !facet) |> plot_fun() + scale_y_continuous(limits = c(0, 1))
p2 <- subset(data, facet) |> plot_fun() + scale_y_continuous(limits = c(-15, 15), position = "right")

p1 + p2 +
  plot_layout(guides = "collect", width = c(3, 1))

第二個但類似的選項是使用ggh4x ，它通過ggh4x::facetted_pos_scales允許單獨設置分面面板的限制。 一個缺點是面板具有相同的寬度。 （我未能使這種方法適用於facet_grid和space="free" ）

library(ggplot2)
library(ggh4x)

data$facet <- data$index %in% "PBIAS"

ggplot(data, aes(x = index, y = value, fill = period)) +
  geom_bar(position = "dodge", stat = "identity") +
  geom_errorbar(aes(ymin = value - sd, ymax = value + sd),
    position = position_dodge(0.9), width = 0.2, alpha = 0.5, size = 1
  ) +
  facet_wrap(~facet, scales = "free") +
  facetted_pos_scales(
    y = list(
      facet ~ scale_y_continuous(limits = c(-15, 15), position = "right"),
      !facet ~ scale_y_continuous(limits = c(0, 1), position = "left")
    )
  ) +
  theme_bw() +
  theme(strip.text.x = element_blank())