r - 使用 ggplot 和 coord_polar 绘制螺旋条形图 (Condegram)

Question

我想在阿基米德螺旋上创建一个条形图，就像讨论的那样 here .

最终目标类似于 this ，但不那么势不可挡。

这是一个示例数据框:

    test <- structure(list(month = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
                                     1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12), 
           year = c(2015, 2015, 2015, 2015, 2015, 2015, 2015, 
                    2015, 2015, 2015, 2015, 2015, 2016, 2016, 
                    2016, 2016, 2016, 2016, 2016, 2016, 2016, 
                    2016, 2016, 2016), 
           value = c(49, 34, 35, 34, 50, 35, 48, 50, 44, 38, 42, 
                   43, 33,30, 42, 43, 58, 55, 47, 36, 35, 53, 
                   61, 59)), 
          .Names = c("month", "year", "value"), 
          class = "data.frame", row.names = c(NA, -24L))

我可以使用以下代码制作条形图:

    ggplot(monthly, aes(x = ym, y = value)) +
      geom_bar(stat = "identity") 

我可以使用以下代码制作螺旋:

    a <- 0   #Any number here & it still looks the same to me...
    b <- 10  #Any number here & it still looks the same to me...
    theta <- seq(0,10*pi, 0.01)
    r <- a + b*theta
    df <- data.frame(x = r*cos(theta), y = r*sin(theta))
    ggplot(df, aes(x,y)) + 
      geom_point(col = 'red')

但是如何(如果有的话)在螺旋上绘制条形图？

这与我所得到的最接近:使用我的数据而不是上面的公式创建螺旋。但我的数据实际上并没有显示...

    d <- ggplot(monthly, aes(x = month, y = month, color = year)) + 
      geom_path(size = 2) + 
      coord_polar() +
      theme_minimal() + 
      theme(legend.position = "none")
    d

Answer 1

一个有趣的问题。为了正确地对条形进行此操作，我们需要使用多边形来正确地考虑每个角的“扭曲”。每个周期的条数越多，该图看起来就会越好，但您可以更改 y 限制以避免中心出现强烈扭曲。您必须想出某种方法来很好地标记 y 轴，但 coord_pold 一开始就不太擅长。

library(tidyverse)

首先，从头开始创建示例 df:

monthly <- 
  expand.grid(month = 1:12, year = factor(unique(monthly$year))) %>% 
  mutate(value = runif(n(), 10, 20),
         y = as.numeric(year) - 1 + (month - 1) / 12) 

或者，从现有的 df 开始工作:

    monthly <- monthly %>%
      mutate(y = as.numeric(year) - 1 + (month - 1) / 12)

继续执行以下操作:

bars <- monthly %>% 
  mutate(value_norm = value / (max(value) * 1.1),
         xmin = month - 0.5,
         xmax = month + 0.5,
         ymin = y,
         ymax = y + value_norm)
# we could plot `bars` here, but things will not line up nicely, since
# the bar will be nice and flat, but it needs to curve with the spiral.

poly <- bars %>% 
  rowwise() %>% 
  do(with(., data_frame(year = year,
                        month = month,
                        x = c(xmin, xmax, xmax, xmin),
                        y = c(ymin - 1/24, 
                              ymin + 1/24, 
                              ymax + 1/24, 
                              ymax - 1/24))))

ggplot(poly, aes(x, y, fill = interaction(month, year))) + 
  geom_polygon(col = 1) +
  coord_polar() +
  ylim(-3, 5) +
  viridis::scale_fill_viridis(discrete = TRUE, option = 'C') +
  scale_x_continuous(breaks = 1:12, labels = month.name) +
  theme_minimal() + 
  theme(legend.position = "none", axis.text.y = element_blank(),
        axis.title = element_blank())

另一种方法是制作螺旋热图:

bars2 <- monthly %>% 
  mutate(xmin = month - 0.5,
         xmax = month + 0.5,
         ymin = y,
         ymax = y + 1)

poly2 <- bars2 %>% 
  rowwise() %>% 
  do(with(., data_frame(value = value,
                        year = year,
                        month = month,
                        x = c(xmin, xmax, xmax, xmin),
                        y = c(ymin - 1/24, ymin + 1/24, ymax + 1/24, ymax - 1/24))))