如何填充 geom_xspline 创建的曲线下的区域

Question

对于后面的数据df和plot，希望能把线条平滑一些，尤其是下图中蓝色矩形标出的尖角部分：

df <- structure(list(date = c("2022-2-1", "2022-2-2", "2022-2-3", "2022-2-4", 
"2022-2-5", "2022-2-6", "2022-2-7", "2022-2-8", "2022-2-9", "2022-2-10", 
"2022-2-11", "2022-2-12", "2022-2-13", "2022-2-14", "2022-2-15", 
"2022-2-16", "2022-2-17"), pct_change = c(4, 4, 4.04, 4.04, 4.04, 
4.44, 4.88, 4.62, 4.8, 5.2, 4.7, 5.06, 4.56, 4.8, 4.32, 4.02, 
4.01)), class = "data.frame", row.names = c(NA, -17L))

df1 <- df %>% 
  mutate_at(vars(-date), funs(./100))
df1 %>% 
  ggplot(aes(x=as.POSIXct(date), y=pct_change)) + 
  geom_line(size=1, alpha=0.7, color='red') +
  geom_hline(yintercept=c(min(df1$pct_change), max(df1$pct_change)), linetype='solid', col='black')

使用ggalt::geom_xspline(spline_shape=0.3, size=1, alpha=0.7, color='red')，我得到了平滑的线，但填充区域并不完美（如您所见，它填充了geom_line(size=1, alpha=0.7, color='red')绘制的原始曲线下方的区域。

library(ggalt)
df1 %>% 
  ggplot(aes(x=as.POSIXct(date), y=pct_change)) + 
  # geom_line(size=1, alpha=0.7, color='red') +
  geom_xspline(spline_shape=0.3, size=1, alpha=0.7, color='red') +
  geom_ribbon(aes(ymin = min(pct_change), ymax = pct_change), fill = 'red', alpha=0.3, position = "identity") +
  # ggforce::stat_bspline(geom = "area", alpha = 0.3, color='red') +
  geom_hline(yintercept=c(min(df1$pct_change), max(df1$pct_change)), linetype='solid', col='black')

如何填充曲线下方的区域，例如 geom_xspline() 创建的曲线，或者我们有其他解决方案？感谢您的提前帮助。

Answer 1

这里有一个替代方案，使用 stat_smooth() 和 geom = "area" 而不是 geom_xspline()，并使用 coord_cartesian 设置绘图限制：

library(tidyverse)

df1 %>% 
  ggplot(aes(x=as.POSIXct(date), y=pct_change)) + 
  stat_smooth(
    geom = "area", 
    size = 1,
    fill = "red", 
    color = "red", 
    alpha = 0.3, 
    span = .3
  ) +
  coord_cartesian(ylim = c(.04, .0525), expand = FALSE)

^{由 reprex package (v2.0.1)} 创建于 2022-03-01

如何填充 geom_xspline 创建的曲线下的区域

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