ggplot2：使用循环绘制几个框

Question

我试图使用循环在ggplot2中绘制一系列框。下面，我已经包含了一个玩具示例。

# Load necessary library
library(ggplot2)

# Height of rectangle
box.size <- 0.5

# Colours for rectangles
my.cols <- c("red", "blue", "purple", "yellow", "green")

# Initialise plot & set limits
p <- ggplot() + xlim(0, 1) + ylim(0, 2.5)

# Loop through and draw boxes
for(i in 1:5){
  # Draw boxes
  p <- p + geom_rect(aes(xmin = 0, xmax = 1, ymin = (i - 1) * box.size, ymax = i * box.size), 
                 fill = my.cols[i])

  # Check that the loop is working
  print(i) 
}

# Plot graph
print(p)

此代码仅绘制最终的矩形，但我无法弄清楚我做错了什么。循环正常运行，因为我包含了要检查的print语句。有人可以指出我的错误并提供解决方案吗？

Answer 1

我同意格雷戈尔。只需创建一个函数，循环或语句来构造基础数据，然后使用ggplot2绘制它。

library(ggplot2)

box.size <- 0.5

df <- data.frame(xmin = rep(0, 5),
           xmax = rep(1,5),
           ymin = (seq(1:5)-1) * box.size,
           ymax = seq(1:5) * box.size,
           fill = c("red", "blue", "purple", "yellow", "green"))

 ggplot(df) +
  geom_rect(aes(xmin = xmin, xmax = xmax, ymin = ymin, ymax = ymax, fill = fill)) +
  scale_fill_identity()

Answer 2

正如Gregor所说，ggplot并不适用于循环。您需要先将坐标设置为数据框：

library(dplyr)
library(ggplot2)
mydf <- data.frame(my.cols, tmp = rep(box.size, 5), i = 1:5)
mydf <- mutate(mydf, ymin = (i - 1) * tmp, ymax = tmp * i)
mydf <- select(mydf, -tmp, -i)

ggplot(mydf) + xlim(0,1) + ylim(0, 2.5) + geom_rect(aes(xmin = 0, xmax = 1, ymin = ymin, ymax = ymax), fill = my.cols)