计算XY极坐标以将对象放置在值标签正下方。

Question

考虑以下数据集：

ig_5 <- data.frame(
  category = c("A", "B", "C", "D", "E", "F"),
  prop = c(0.1, 0.2, 0.15, 0.25, 0.05, 0.25)
) %>%
  mutate(lab.ypos = cumsum(prop) - 0.5*prop)

我使用以下代码创建了一个甜甜圈图表：

ggplot(ig_5, aes(x = 2, y = prop, fill = prop)) +
  geom_bar(stat = "identity", color = "white") +
  coord_polar(theta = "y", start = 0) +
  geom_text(aes(y = lab.ypos, label = prop), color = "black", size = 5) +
  xlim(.5, 2.5)

如您所见，值标签放置在每个类别的中间。现在，我需要将图形放置在每个值标签的正下方。我不能只是将新对象粘贴到值上，因为文本和图形的颜色不同。因此，我想象应该有一种方法可以使用值标签的坐标（x = 2，y = lab.ypos = cumsum（prop）-0.5 * prop）来定位所需的图形。

我使用geom_label添加了新图形，并给它一个与值标签的XY坐标成比例的位置。然而，我还没有成功。这是我尝试过的一个示例。

ig_5 <- data.frame(
  category = c("A", "B", "C", "D", "E", "F"),
  prop = c(0.1, 0.2, 0.15, 0.25, 0.05, 0.25)) %>%
  mutate(lab.ypos = cumsum(prop) - 0.5*prop, 
         lab.ypos2 = cumsum(prop) + 0.3*prop)

 
ggplot(ig_5, aes(x = 2, y = prop, fill = prop)) +
  geom_bar(stat = "identity", color = "white") +
  coord_polar(theta = "y", start = 0) +
  geom_text(aes(y = lab.ypos, label = prop), color = "black", size = 5) +
  geom_label(aes(y = lab.ypos,
                 x = c(1.85, 2.1, 2.2, 1.95, 1.8, 1.85),
                 label = "figure"), 
             color = 'red') +
  xlim(.5, 2.5) 

而我得到的结果是：

- Santiago Valdivieso

---

多好且可重现的第一个问题！欢迎来到本站！ - Gregor Thomas

Answer 1

我有点偏见，但我认为geomtextpath在这里很有效：

library(geomtextpath)

ggplot(ig_5, aes(x = 2, y = prop, fill = prop)) +
  geom_bar(stat = "identity", color = "white", linewidth = 1.5) +
  coord_polar(theta = "y", start = 0) +
  geom_textpath(aes(y = lab.ypos, label = prop, group = category), 
                color = "black", size = 8, angle = 90, vjust = 1) +
  geom_labelpath(aes(y = lab.ypos, label = "figure", group = category), 
                color = "red4", size = 6, angle = 90, vjust = -1.5) +
  scale_fill_gradientn(colours = c("lightyellow", "gold", "orange")) +
  xlim(.5, 2.5) +
  theme_void(base_size = 20)

- Allan Cameron

Answer 2

我们可以滥用vjust来垂直地调整标签，超出正常的0到1范围。这将在视觉上垂直移动标签，而不考虑坐标系。适用的数量可能取决于输出的尺寸 - 只需尝试值，直到它起作用 :)

ggplot(ig_5, aes(x = 2, y = prop, fill = prop)) +
  geom_bar(stat = "identity", color = "white") +
  coord_polar(theta = "y", start = 0) +
  geom_text(aes(y = lab.ypos, label = prop), color = "black", size = 5) +
  geom_label(aes(y = lab.ypos,
                 label = "figure"), 
             vjust = 1.5,
             color = 'red') +
  xlim(.5, 2.5)

- Gregor Thomas

Answer 3

另一个选择是使用ggtext :: geom_richtext，通过label.margin参数允许“移动”标签半个值标签的大小，结合使用vjust = 1应该确保标签放置在值标签正下方。

library(ggplot2)

ggplot(ig_5, aes(x = 2, y = prop, fill = prop)) +
  geom_bar(stat = "identity", color = "white") +
  coord_polar(theta = "y", start = 0) +
  geom_text(aes(y = lab.ypos, label = prop),
    color = "black", size = 5
  ) +
  ggtext::geom_richtext(
    aes(
      y = lab.ypos,
      label = "figure"
    ),
    color = "red",
    label.margin = unit(2.5, "mm"),
    vjust = 1
  ) +
  xlim(.5, 2.5)

- stefan