保持堆积图中的因子水平（ggplot）-Java 学习之路

在ggplot中对因子水平进行排序是一个常见问题，并且有很多关于它的帖子（例如，Avoid ggplot sorting the x-axis while plotting geom_bar()） .

这可能是重复的，但我没有遇到过这种特殊情况 .

我试图在堆积条形图中维持X轴变量（“柱面”）的顺序 . 这是一个玩具的例子 . 我将下面的变量转换为强调X轴上的字母顺序，即使该变量（柱面）在数据帧中早先设置为“Four cyl”，“Six cyl”和“Eight cyl”的显式排序 .

我究竟做错了什么？

mtcars <- mtcars %>% 
  mutate(cylinders = case_when(cyl == 4 ~ "Four cyl",
                               cyl == 6 ~ "Six cyl",
                               cyl == 8 ~ "Eight cyl"),
         cylinders = reorder(cylinders, cyl, mean)) %>% 
  mutate(engine = case_when(vs == 1 ~ "Manual",
                            vs == 0 ~ "Automatic"))

str(mtcars$cylinders)
levels(mtcars$cylinders)  # [1] "Four cyl"  "Six cyl"   "Eight cyl"
class(mtcars$cylinders)

facet_test <- function(df, gathvar) {

  gath <- enquo(gathvar)

  df %>% 
    select(cylinders, !!gath) %>%
    gather(key, value, -!!gath) %>%
    count(!!gath, key, value) %>%
    group_by(value) %>%
    mutate(perc = round(n/sum(n), 2) * 100) %>%  
    ggplot(aes(x = value, y = perc, fill = !!gath)) +
      geom_bar(stat = "identity")
}

facet_test(df = mtcars, gathvar = engine)

enter image description here

1 回答

感谢评论和@alistaire在这篇文章（https://stackoverflow.com/a/39157585/8453014），我得到了一个解决方案 . 问题是 gather 将因素强制转换为字符 .

Simple scenario 正如@aosmith建议的那样，在 gather 之后使用 mutate(value = factor(value, levels = levels(mtcars$cylinders)) ) .

Complex example with multiple variables 重要的方面是1）定义因子水平（无论是在函数内部还是外部）和2）将水平应用于"value"列 .

这是一个更复杂的示例，显示使用三个变量并应用facet_wrap并排查看图：

facet_test <- function(df, gathvar, legend_title) {
  gath <- enquo(gathvar)

# next two lines can go inside or outside of the function
  levels_cyl <- c("Four cyl", "Six cyl", "Eight cyl")
  levels_gears <- c("Three", "Four", "Five")

  df %>% 
    select(cylinders, gears, !!gath) %>%
    gather(key, value, -!!gath) %>%
    count(!!gath, key, value) %>%
    ungroup() %>% 
    mutate(value = factor(value, levels = unique(c(levels_cyl, levels_gears), 
                                                         fromLast = TRUE))) %>% 
    arrange(key, value) %>%  
    ggplot(aes(x = value, y = n, fill = !!gath)) +
      geom_bar(stat = "identity") +
      facet_wrap(~ key, scales = "free_x")
}

facet_test(df = mtcars, gathvar = engine)

[
correct plot with factor levels in pre-defined order1

回复于 2024-04-20T01:25:57+08:00

保持堆积图中的因子水平（ggplot）

1 回答

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