在第二个 y 轴和矩形背景上使用频率（计数）而不是密度的山脊线图

Question

我想使用 ggplot2 和 ggridges 将第二个 y 轴上的频率添加到脊线图

我找到了一个使用 geom_text (https://rdrr.io/cran/ggridges/man/stat_binline.html) 将频率添加为数字的教程，但是，我更愿意将它们添加为第二个 y 轴。

当然，我非常感谢 ggridges 之外的解决方案以获得类似的情节。

示例数据：

library(ggplot2)
library(ggridges)
library(lubridate)

# datapoints
data_timepoint <- data.frame(type=factor(c("A","B","C","D")),
                             start=as.Date(c("1990-01-01","2000-01-01","2010-01-01","2012-01-01")),
                             stop=as.Date(c(rep("2022-01-01",4))))

                             
                             
# frequencies                             
data_freq <- data.frame(type=c("A","A","B","C","D","D","D"),
                        year=ymd(year(as.Date(c("1991-01-01","1991-01-01","2005-01-01","2016-01-01","2013-01-01","2013-01-01","2015-01-01"))),truncated=2L))
                                 




# plot
ggplot(data_timepoint) +
  geom_rect(aes(xmin=start, xmax=stop,
                ymin=type, ymax=as.numeric(type)+0.9), fill="lightblue") +
  geom_density_ridges(data=data_freq, aes(x=year,y=type),stat = "binline",
                      bins = 1, scale = 0.95, draw_baseline = FALSE, alpha=.5, binwidth=10,center=20) +
  scale_x_date(date_breaks = "1 year",date_labels = "%Y") +
    theme(axis.text.x = element_text(angle = 90),
        axis.text.y = element_text(vjust = -2)) +
  labs(title="",y="Type",x="Year")

^{由reprex package (v2.0.1) 于 2022-06-03 创建}

期望的输出：

Answer 1

从技术上讲，您实际上并没有第二个 y 轴 - 您只想显示频率而不是密度。您通常可以通过使用..count.. 或使用更新的语法after_stat(count) 作为您的审美来显示频率。 ggridges 似乎没有算作计算的统计数据 - 因此可能会伪造您的 ggridges 外观。

示例改编自 ?geom_density_ridges

library(ggplot2)

## swap x and y
ggplot(diamonds, aes(price)) +
## use y = after_stat(count) to show your frequency
  geom_density(aes(y =after_stat(count))) +
## change the y axis position to the right
  scale_y_continuous(expand = c(0.01, 0), position = "r") +
  scale_x_continuous(expand = c(0.01, 0)) +
## add facet, and put label to the left
  facet_wrap(~cut, ncol = 1, strip.position = "l") 

^{由reprex package (v2.0.1) 于 2022-06-03 创建}

如果你更进一步，让刻面重叠（这是脊图的原理：密度图的重叠刻面），你会发现通过在经典脊图上添加轴指南，将是脊（你的小平面）之间的那些指南的重叠。这看起来不太好。

这与你的 stat 无关，而且 stat = "binline" 也会发生

p <- ggplot(diamonds, aes(price)) +
  geom_density(aes(y = ..count..)) +
  scale_y_continuous(expand = c(0.01, 0), position = "r") +
  scale_x_continuous(expand = c(0.01, 0)) +
  facet_wrap(~cut, ncol = 1, strip.position = "l")  +
## let the facets overlap (make background and strip transparent)
  theme(panel.spacing.y = unit(-.3, "in"), 
        strip.background = element_blank(),
        panel.background = element_blank(), 
        panel.grid.major = element_blank())

cowplot::stamp_bad(p)

要添加所需的矩形注释，您的方法非常好。数据实际上是否像您的示例中那样结构化，或者您是否刚刚基于第一个框架预先创建了第二个框架？ （这样做会很棒而且做得很好）

代码中还有一些 cmets

   
ggplot() +
## use different y - slightly depending on your desired look 
geom_rect(data = data_timepoint, aes(xmin=start, xmax=stop, ymin=0, ymax=1), fill="lightblue") +
geom_histogram(data= data_freq, aes(year)) +
## added pretty labels
scale_y_continuous(expand = c(0, 0), position = "r", breaks = scales::breaks_pretty(n = 2)) +
## keep x as date
scale_x_date(expand = c(0, 0)) +
facet_wrap(~type, ncol = 1, strip.position = "l")