Aim
我正在尝试填充 R 中 ggplot 生成的图中两条线之间的区域。我想用与水平线下方不同的颜色填充水平线上方的线之间的所有内容。
我成功地用单一颜色填充了两条线之间的所有内容，但是，我无法用两种不同的颜色区分垂直线的上方和下方。
Code
set.seed(123)
# Load packages
library(tidyverse)
# Create sample dataframe
df <- data.frame(x=seq(1,50,1),y=runif(50, min = 0, max = 10))
# Generate plot
ggplot(data = df, aes(x = x, y = y)) +
geom_line() +
geom_hline(yintercept = 5) +
theme_classic() +
geom_ribbon(aes(ymin=5,ymax=y), fill="blue")
Question
如何用不同的颜色填充水平线上方和下方的空间？
您可以计算两条线相交点的坐标并将其添加到数据框中：
m <- 5 # replace with desired y-intercept value for the horizontal line
# identify each run of points completely above (or below) the horizontal
# line as a new section
df.new <- df %>%
arrange(x) %>%
mutate(above.m = y >= m) %>%
mutate(changed = is.na(lag(above.m)) | lag(above.m) != above.m) %>%
mutate(section.id = cumsum(changed)) %>%
select(-above.m, -changed)
# calculate the x-coordinate of the midpoint between adjacent sections
# (the y-coordinate would be m), & add this to the data frame
df.new <- rbind(
df.new,
df.new %>%
group_by(section.id) %>%
filter(x %in% c(min(x), max(x))) %>%
ungroup() %>%
mutate(mid.x = ifelse(section.id == 1 |
section.id == lag(section.id),
NA,
x - (x - lag(x)) /
(y - lag(y)) * (y - m))) %>%
select(mid.x, y, section.id) %>%
rename(x = mid.x) %>%
mutate(y = m) %>%
na.omit())
使用此数据框，您可以定义两个单独的geom_ribbon具有不同颜色的层。下面的结果比较（注：我还添加了一个geom_point图层用于插图，并更改了颜色，因为原件中的蓝色有点刺眼......）
p1 <- ggplot(df,
aes(x = x, y = y)) +
geom_ribbon(aes(ymin=5, ymax=y), fill="dodgerblue") +
geom_line() +
geom_hline(yintercept = m) +
geom_point() +
theme_classic()
p2 <- ggplot(df.new, aes(x = x, y = y)) +
geom_ribbon(data = . %>% filter(y >= m),
aes(ymin = m, ymax = y),
fill="dodgerblue") +
geom_ribbon(data = . %>% filter(y <= m),
aes(ymin = y, ymax = m),
fill = "firebrick1") +
geom_line() +
geom_hline(yintercept = 5) +
geom_point() +
theme_classic()
