通过堆积条形图中的数字变量对具有分类变量的列进行排序 [英] sort columns with categorical variables by numerical varables in stacked barplot

问题描述

我有一个包含数字(百分比)和分类变量的数据框.我想生成一个堆积的条形图(使用ggplot2)，并用数值变量对列(类别变量)进行排序.

I have a dataframe containing numerical (percentages) and categorical variables. I'd like to produce a stacked barplot (using ggplot2) with the colums (categorical variables) sorted by the numerical variable.

我尝试过:

如何控制ggplot2上使用标识的堆积条形图

和这个:

https://community.rstudio.com/t/a-tidy-way-to-order-stacked-bar-chart-by-fill-subset/5134

但是我不熟悉因素，我想了解更多.

but I am not familiar with factors and I'd like to understand more.

# Reproduce a dummy dataset
perc <- c(11.89, 88.11, 2.56, 97.44, 5.96, 94.04, 6.74, 93.26)
names <- c('A', 'A', 'B', 'B', 'C', 'C', 'D', 'D')

df <- data.frame(class = rep(c(-1, 1), 4), 
                 percentage = perc, 
                 name = names)

# Plot
ggplot(df, aes(x = factor(name), y = percentage, fill = factor(class))) +
  geom_bar(stat = "identity") +
  scale_fill_discrete(name = "Class") +
  xlab('Names')

此代码生成一个图，其条形由变量名称"排序.我想按变量百分比"对其进行排序.即使我手动订购数据框，结果图也一样.

This code produces a plot whose bars are ordered by the variable "names". I'd like to order it by the variable "percentage". Even if I manually order the dataframe, the resulting plot is the same.

推荐答案

这里的问题是，给定类别( name )的所有百分比实际上加起来为100％.因此，按百分比排序通常无法通过 aes(x = reorder(name，percent)，y = percent)来实现，

The issue here is that all your percentages for a given category (name) in fact add up to 100%. So sorting by percentage, which is normally achieved via aes(x = reorder(name, percentage), y = percentage), won’t work here.

相反，您可能想按class = 1(或class = -1)的数据的百分比排序.这样做需要一些技巧:使用 ifelse 为 class == 1 的行选择百分比.对于所有其他行，选择值0:

Instead, you probably want to order by the percentage of the data that has class = 1 (or class = -1). Doing this requires some trickery: Use ifelse to select the percentage for the rows where class == 1. For all other rows, select the value 0:

ggplot(df, aes(x = reorder(name, ifelse(class == 1, percentage, 0)), y = percentage, fill = factor(class))) +
  geom_bar(stat = "identity") +
  scale_fill_discrete(name = "Class") +
  xlab('Names')

您可能只想执行 reorder 指令以查看发生的情况:

You might want to execute just the reorder instruction to see what’s going on:

reorder(df$name, ifelse(df$class == 1, df$percentage, 0))
# [1] A A B B C C D D
# attr(,"scores")
#      A      B      C      D
# 44.055 48.720 47.020 46.630
# Levels: A D C B

如您所见，您的姓名根据每个类别的平均百分比重新排序(默认情况下， reorder 使用平均值；

As you can see, your names got reordered based on the mean percentage for each category (by default, reorder uses the mean; see its manual page for more details). But the "mean" we calculated was between each name’s percentage for class = 1, and the value 0 (for class ≠ 1).

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