在 ggplot + coord_polar 中自定義 x 軸標簽位置

Question

我正在使用coord_polar以時鍾圖的形式顯示物種豐度隨時間的變化，如下所示

year<-c(2017, 2018, 2019) # observation dates
sp1<-c(39,55,85)
sp2 <-c(100, 75, 65)
sp3 <-c(32,57,42)

df <-data.frame(year, sp1, sp2, sp3) 
d <- df %>% 
  pivot_longer(!year, names_to = "species", values_to = "cover") 

plot <-ggplot(d, aes(year, cover, color = species)) +
  geom_line(size = 2) + coord_polar() + theme_classic() +
  theme(text = element_text(size = 18), 
        legend.text = element_text(face = "italic"), 
        #axis.text.x=element_blank(), # remove all x axis labels in polar_coord
        #axis.text.x=element_text(angle = 25), # rotates angle, but does not increase distance between labels. 
        legend.title=element_blank(), 
        legend.position="right") +
  scale_x_continuous(breaks=c(2019, 2018, 2017)) # this customizes the x-axis labels to be my 
            # exact observation dates. List order places 2019 at the 11:59 "clock" position, 
            # and 2017 at the 12:01 "clock" position)
plot

我看到的問題是 2017 年和 2019 年的標簽是如此接近，以至於在視覺上很難將它們解釋為時鍾的開始和停止。 有沒有辦法增加它們之間的間距？ （見下面的示例圖片）

我一直在嘗試使用上面評論的theme(axis.text.x = ...)進行自定義，但到目前為止它並沒有達到我想要的效果。 還有其他建議嗎？ 謝謝！

Answer 1

您可以簡單地調整 x 軸上的中斷和標簽。 我認為它還可以改善帶有彎曲標簽的外觀，也許還有一些年份分隔符：

library(geomtextpath)

ggplot(d, aes(year, cover, color = species)) +
  geom_rect(data = data.frame(y = c(2017, 2017 + 2/3, 2018 + 1/3)),
            aes(ymax = Inf, ymin = -Inf, xmin = y, xmax = y + 2/3),
            inherit.aes = FALSE, alpha = 0.05, color = "gray75") +
  geom_line(size = 2) + 
  coord_curvedpolar() + 
  theme_classic() +
  scale_x_continuous(breaks = c(2017.33, 2018, 2018.67), labels = 2017:2019) +
  theme(text = element_text(size = 18), 
        legend.text = element_text(face = "italic"),
        legend.title=element_blank(), 
        legend.position="right",
        axis.line.x.bottom = element_blank()) 

Answer 2

使用注釋可能更容易？

ggplot(d, aes(year, cover, color = species)) +
  geom_line(size = 2) + 
  annotate("text", size = 6,  label = year,
           x = c(2017.1, 2018, 2018.9),
           y = c(110, 90, 110)) +
  coord_polar() + 
  theme_classic() +
  theme(text = element_text(size = 18), 
        legend.text = element_text(face = "italic"), 
        #axis.text.x=element_blank(), # remove all x axis labels in polar_coord
        #axis.text.x=element_text(angle = 25), # rotates angle, but does not increase distance between labels. 
        legend.title=element_blank(), 
        legend.position="right") +
  scale_x_continuous(labels = NULL)