是否可以使用单位设置geom_bar（）宽度

Question

在geom_bar（）中，将参数“ width =”设置为单位（例如“ mm”），而不设置数据分辨率的百分比（默认值）？

当我尝试使用此代码时：

df<-data.frame("x" = rep(c("a","b","c","d"), times = 3),
               "y" = c(6,22,10,7,50,68,53,21,44,10,37,72),
               "group" = rep(c("gp1","gp2","gp3"),each=4))
ggplot(data = df,aes(x = x, y = y, fill = group))+
  geom_bar(aes(x = x, y = y, fill = group),
           width = unit(5, "mm"),
           stat = "identity")

它返回Error in Ops.unit(width, 2) : operator '/' not meaningful for units