ggplot：在geom_violin（）上添加理论范围

Question

让我们说我们观察了两种甲虫。我们想使用geom_violin（）比较它们的大小，如下所示：

df = data.frame(species=rep(c('species_a','species_b'),3), size=c(1,1.5,1.2,1.8,1.1,1.9))
ggplot(df, aes(x=species, y=size)) + geom_violin()

了解物种的预期大小范围是[0.8,1.8]，物种的预期大小范围是[1.2,1.8] ...

ranges = list(species_a=c(0.8,1.8), species_b=c(1.2,1.8))

如何在图表上轻松添加此范围（例如灰色形状）？

Answer 1

将范围放在具有物种名称和最小/最大值的单独数据框中

ranges = data.frame(species=c('species_a','species_b'), 
                    rmin=c(0.8,1.2),rmax=c(1.2,1.8))
ranges

    species rmin rmax
1 species_a  0.8  1.8
2 species_b  1.2  1.8

然后使用geom_rect()的新数据框来制作位于geom_violin()下方的区域。 geom_blank()用于根据原始数据帧生成x轴。

ggplot(df, aes(x=species, y=size))  + geom_blank() + 
  geom_rect(data=ranges,aes(xmin=as.numeric(species)-0.45,
                            xmax=as.numeric(species)+0.45,
                            ymin=rmin,ymax=rmax),inherit.aes=FALSE)+
  geom_violin()

Answer 2

你可以试试这个：

# first, create data frame from list 'ranges'
df2 <- setNames(object = do.call(rbind.data.frame, ranges), nm = c("min_size", "max_size"))
df2$species <- rownames(df2)

# plot violins with 'df', and ranges with 'df2'.
# Set colour and size according to your own "data-ink ratio" preferences.
ggplot(data = df, aes(x = species)) +
  geom_violin(aes(y = size)) +
  geom_linerange(data = df2, aes(ymax = max_size, ymin = min_size), colour = "grey", size = 3)