Question

使用Dr. Evers suggestion使用ggridges对密度曲线下的区域进行遮挡效果很好。但是，我发现密度曲线可能是欺骗性的，因为它们意味着数据存在的时候不存在。因此，我想我会用普通的直方图来尝试这种着色技术。

然而，当我尝试使用直方图时，阴影有点偏。这是为什么？

library(tidyverse)
install.packages("ggridges", dependencies=TRUE)  # there are many
library(ggridges)
 t2 <-   structure(list(Date = c("1853-01", "1853-02", "1853-03", "1853-04", 
"1853-05", "1853-06", "1853-07", "1853-08", "1853-09", "1853-10", 
"1853-11", "1853-12", "1854-01", "1854-02", "1854-03", "1854-04", 
"1854-05", "1854-06", "1854-07", "1854-08", "1854-09", "1854-10", 
"1854-11", "1854-12"), t = c(-5.6, -5.3, -1.5, 4.9, 9.8, 17.9, 
18.5, 19.9, 14.8, 6.2, 3.1, -4.3, -5.9, -7, -1.3, 4.1, 10, 16.8, 
22, 20, 16.1, 10.1, 1.8, -5.6), year = c("1853", "1853", "1853", 
"1853", "1853", "1853", "1853", "1853", "1853", "1853", "1853", 
"1853", "1854", "1854", "1854", "1854", "1854", "1854", "1854", 
"1854", "1854", "1854", "1854", "1854")), row.names = c(NA, -24L
), class = c("tbl_df", "tbl", "data.frame"), .Names = c("Date", 
"t", "year"))


gg <- ggplot(t2, aes(x = t, y = year)) +
      geom_density_ridges(stat = "binline", bins = 10, scale = 0.8, 
                      draw_baseline = TRUE) +
      theme_ridges()

# Build ggplot and extract data
d <- ggplot_build(gg)$data[[1]]

# Add geom_ribbon for shaded area
gg +
  geom_ribbon(
    data = transform(subset(d, x >= 10), year = group),
    aes(x, ymin = ymin, ymax = ymax, group = group),
    fill = "red",
    alpha = 1.0)

Answer 1

确实发生了一些奇怪的事情。请参阅下面的＆＃34;结论＆＃34;。

如果我们仅绘制gg：
```
 gg;
```

如果我们绘制gg加上一个应与gg的跟踪相对应的阶梯步骤：

  gg +
      geom_step(
          data = d, 
          aes(xmax, ymax, group = group), 
          direction = "vh", col = "red",  size = 2);

因此，以某种方式添加geom_step更改gg。我不明白这是怎么回事。您可以看到geom_step（红色曲线）实际上与直方图的轨迹相对应，在单独绘制gg时（参见第一个图）。

Answer 2

如果您愿意调整大小并移动垃圾箱以使垃圾箱边界恰好位于您的分界线（此处为10），则以下情况有效。

ggplot(t2, aes(x = t, y = year, fill = ifelse(..x..>=10, ">= 10", "< 10"))) +
  geom_density_ridges_gradient(stat = "binline", binwidth = 3,
                               center = 8.5, scale = 0.8, 
                               draw_baseline = TRUE) +
  theme_ridges() +
  scale_fill_manual(values = c("gray70", "red"), name = NULL)

您观察效果的原因是因为x轴在第一个和第二个绘图之间发生变化，x轴范围会影响绘制二进制位的方式。有两种解决方案：您可以修复x轴范围，也可以通过center和binwidth而不是bins来定义容器。（在我看来，无论你如何对待x轴，第二种选择总是无论如何都是首选。）

首先，修复x轴范围：

gg <- ggplot(t2, aes(x = t, y = year)) +
  geom_density_ridges(stat = "binline", bins = 10, scale = 0.8, 
                      draw_baseline = TRUE) +
  theme_ridges() +
  scale_x_continuous(limits = c(-12, 28)) # this is where the change is

# Build ggplot and extract data
d <- ggplot_build(gg)$data[[1]]

# Add geom_ribbon for shaded area
gg +
  geom_ribbon(
    data = transform(subset(d, x >= 10), year = group),
    aes(x, ymin = ymin, ymax = ymax, group = group),
    fill = "red",
    alpha = 1.0)

其次，替代bin定义：

gg <- ggplot(t2, aes(x = t, y = year)) +
  geom_density_ridges(stat = "binline",
                      binwidth = 3, center = 8.5, # this is where the change is
                      scale = 0.8, draw_baseline = TRUE) +
  theme_ridges()

# Build ggplot and extract data
d <- ggplot_build(gg)$data[[1]]

# Add geom_ribbon for shaded area
gg +
  geom_ribbon(
    data = transform(subset(d, x >= 10), year = group),
    aes(x, ymin = ymin, ymax = ymax, group = group),
    fill = "red",
    alpha = 1.0)

ggridges直方图（stat = binline）下的阴影面积如何？

2 个答案: