ggplot2:添加框(goem_rect?)下面是基于值的颜色渐变图

Question

我在试着画出火灾后每年出苗的苗木数量。苗木的数量在y轴上，也就是火在x轴上的年份。我想在这个图下面添加一个方框或矩形，以显示另一个变量(假设降雨量)的值每年都会变化。如下所示：

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我已经设法做到了这一点，用geom_rect()为每年添加了一个单独的矩形，但是有没有一种方法可以不使用10个单独的矩形呢？特别是这样我只需要指定一次颜色修改，而不是在10个不同的geom_rect()调用中？？

这两篇较早的文章(one，two)帮助我走到了今天，但我只想用几行代码就能做到这一点。我还没能让scale_fill_gradient()正常工作，但也许这是解决方案的一部分？

此处的数据：

yr_since <- c(1:10)
density <- c(23, 58, 68, 126, 154, 103, 90, 94, 73, 59)
rain <- c(3, 6, 8, 5, 8, 3, 4, 4, 6, 2)
data <-as.data.frame(cbind(yr_since, density, rain))

当前(可怕的)代码如下：

plot <- ggplot(data = data, aes(x = yr_since)) +
  geom_col(aes(y=density), width = 0.95) +
  scale_x_discrete(expand = c(0,0), drop=FALSE, labels = yr_since) +
  labs(x = "Years since fire", y = "Density (stems/ha)") 

plot + 
  geom_rect(data=data,
            aes(xmin = 0.5, ymin = -5, 
                xmax = 1.5, ymax = 0,
                fill = rain[1])) +
  geom_rect(data=data,
            aes(xmin = 1.5, ymin = -5, 
                xmax = 2.5, ymax = 0,
                fill = rain[2])) +
  geom_rect(data=data,
            aes(xmin = 2.5, ymin = -5, 
                xmax = 3.5, ymax = 0,
                fill = rain[3])) +
  geom_rect(data=data,
            aes(xmin = 3.5, ymin = -5, 
                xmax = 4.5, ymax = 0,
                fill = rain[4])) +
  geom_rect(data=data,
            aes(xmin = 4.5, ymin = -5, 
                xmax = 5.5, ymax = 0,
                fill = rain[5])) +
  geom_rect(data=data,
            aes(xmin = 5.5, ymin = -5, 
                xmax = 6.5, ymax = 0,
                fill = rain[6])) +
  geom_rect(data=data,
            aes(xmin = 6.5, ymin = -5, 
                xmax = 7.5, ymax = 0,
                fill = rain[7])) +
  geom_rect(data=data,
            aes(xmin = 7.5, ymin = -5, 
                xmax = 8.5, ymax = 0,
                fill = rain[8])) +
  geom_rect(data=data,
            aes(xmin = 8.5, ymin = -5, 
                xmax = 9.5, ymax = 0,
                fill = rain[9])) +
  geom_rect(data=data,
            aes(xmin = 9.5, ymin = -5, 
                xmax = 10.5, ymax = 0,
                fill = rain[10]))

Answer 1

您可以使用y的固定负值进行额外的geom_col调用来添加它们

library(ggplot2)

data <- data.frame(yr_since = c(1:10),
                   density = c(23, 58, 68, 126, 154, 103, 90, 94, 73, 59),
                   rain = c(3, 6, 8, 5, 8, 3, 4, 4, 6, 2))

ggplot(data, aes(x = yr_since, y = density)) +
    geom_col(width = 0.95) + 
    geom_col(aes(y = -5, fill = rain), width = 1) + 
    scale_x_continuous(breaks = data$yr_since, expand = c(0, 0)) + 
    scale_y_continuous(expand = c(0, 0), limits = c(-5, max(data$density) * 1.05)) + 
    labs(x = "Years since fire", 
         y = "Density (stems/ha)") 

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根据需要进行调整。