R - 根据条件求和并合并列

Question

我有以下数据框:

df1 <- data.frame( id = c(1,2,2,3),
                   word = c("house, garden, flower", "flower, red", "garden, tree, forest", "house, window, door, red"),
                   value = c(10,12,20,5),
                   stringsAsFactors = FALSE
)

现在我想根据 id 合并行。因此，如果存在重复的 id，则应合并列 word 中的值，并对列值进行求和。这意味着 df 应如下所示:

id | word                              | value
1  | house, garden, flower             | 10
2  | flower, red, garden, tree, forest | 32
3  | house, window, door, red          | 5

有人知道如何解决这个问题吗？

Answer 1

以 R 为基数:

df1 <- data.frame( id = c(1,2,2,3),
                   word = c("house, garden, flower", "flower, red", "garden, tree, forest", "house, window, door, red"),
                   value = c(10,12,20,5),
                   stringsAsFactors = FALSE
)

want <- data.frame(id = unique(df1$id),
                   word = tapply(df1$word, df1$id, paste, collapse = ", "),
                   value = tapply(df1$value, df1$id, sum))
want

  id                              word value
1  1             house, garden, flower    10
2  2 flower, red, garden, tree, forest    32
3  3          house, window, door, red     5