如何在 R 中为多个变量创建计数列

Question

我有一个看起来像这样的数据集。每个事件都有 1-3 个标签，标签中列出了颜色。所有颜色都可以出现在 3 个标签列中的任何一个中。一个项目可以有多个事件。

> data.frame(item = c(1,1,2,3,4,4,4,5), event = seq(1,8), 
+            tag1 = c("red","red","blue","green","red","yellow","black","purple"), 
+            tag2 = c("blue","NA","NA","yellow","orange","NA","purple","red"), 
+            tag3 = c("NA","NA","NA","red","magenta","NA","red","green"))
  item event   tag1   tag2    tag3
1    1     1    red   blue      NA
2    1     2    red     NA      NA
3    2     3   blue     NA      NA
4    3     4  green yellow     red
5    4     5    red orange magenta
6    4     6 yellow     NA      NA
7    4     7  black purple     red
8    5     8 purple    red   green

我想要做的是转换数据，以便每个项目都有一行，然后，每种可能的颜色都有一列，值是该项目是否曾被标记过。

例如：

| Item| Red | Blue | Green | etc |
| 1   | 1   | 1    | 0     | 0   |
| 2   | 0   | 0    | 1     | 0   | 

我不想手动创建列，因为在我的实际代码中，大约有 800 种不同的“颜色”。

我正在与 tidyverse 合作尝试解决这个问题，但我对其他使它更容易的软件包开放。

运行时确实很重要，因为我在数据集中有超过 1000 万个事件。

Answer 1

library(tidyverse)

df %>%
  na_if("NA") %>% 
  pivot_longer(cols = starts_with("tag")) %>% 
  drop_na() %>% 
  count(item, value) %>% 
  pivot_wider(names_from = value, 
              values_from = n, 
              values_fill = 0)

# A tibble: 5 × 9
   item  blue   red green yellow black magenta orange purple
  <dbl> <int> <int> <int>  <int> <int>   <int>  <int>  <int>
1     1     1     2     0      0     0       0      0      0
2     2     1     0     0      0     0       0      0      0
3     3     0     1     1      1     0       0      0      0
4     4     0     2     0      1     1       1      1      1
5     5     0     1     1      0     0       0      0      1

要求：

df %>%
  na_if("NA") %>% 
  pivot_longer(cols = starts_with("tag")) %>% 
  drop_na() %>% 
  count(item, value) %>% 
  pivot_wider(names_from = value, 
              values_from = n, 
              values_fill = 0) %>% 
  mutate(grey = 0, 
         white = 0)

Answer 2

使用来自base R的table

table(df1$item[row(df1[-c(1:2)])], unlist(df1[-(1:2)]))

-输出

    black blue green magenta orange purple red yellow
  1     0    1     0       0      0      0   2      0
  2     0    1     0       0      0      0   0      0
  3     0    0     1       0      0      0   1      1
  4     1    0     0       1      1      1   2      1
  5     0    0     1       0      0      1   1      0

---

如果我们想要缺失的组合，请创建一个 factor 列并指定 levels

colors <- factor(unlist(df1[-(1:2)]), levels = c("black", "blue", 
   "gray", "green", "magenta", "orange", "purple", "red", "yellow", "white"))
items <- df1$item[row(df1[-c(1:2)])]
table(items, colors)

-输出

    colors
items black blue gray green magenta orange purple red yellow white
    1     0    1    0     0       0      0      0   2      0     0
    2     0    1    0     0       0      0      0   0      0     0
    3     0    0    0     1       0      0      0   1      1     0
    4     1    0    0     0       1      1      1   2      1     0
    5     0    0    0     1       0      0      1   1      0     0