如何在R中的数据帧中存储向量

Question

我正在尝试通过 for 循环创建一个数据框，并尝试为数据框的每一行添加一个向量。

行是人，列是名称类别和点类别。

例如，我正在尝试使用类似...

Name  Points
Susie c(12,45,23)
Bill  c(13,24,12,89)
CJ    c(12)

到目前为止我的代码看起来像

names_list <-c("Susie","Bill","CJ")
result = data.frame()

for (name in names_list){
    listing = .....
    frame = data.frame(name,listing)
    names(frame) = c("name","list")
    result <- rbind(result,frame)
}

列表恰好是与该名称相关联的点。但是，它不是为包含所有点的每个名称创建 1 行，而是为每个点创建具有相同名称的多行。

结果看起来像

1 Susie    12
2 Susie    45
3 Susie    23
4  Bill    13
5  Bill    24
6  Bill    12
7  Bill    89
8    CJ    12

Answer 1

The specific problem you've encountered is due to data.frame flattening any list inputs. This can be prevented using the identify function I. For example,

data.frame(a = 1, b = list(c("a", "b")))

doesn't do what you want, but

data.frame(a = 1, b = I(list(c("a", "b"))))

does. A discussion of this behavior and some alternatives are available at http://r4ds.had.co.nz/many-models.html#list-columns-1

You can use I to produce the desired result using your example as well:

names_list <-c("Susie","Bill","CJ")
points <- list(c(12,45,23),
               c(13,24,12,89),
               12)

result = data.frame()

for (i in 1:length(names_list)){
    frame = data.frame(names_list[[i]], I(points[i]))
    names(frame) = c("name","list")
    result <- rbind(result,frame)
}

though as pointed out in the comments, there are better ways to do it. All you really need is

data.frame(
    name = names_list,
    points = I(points))

Answer 2

我不知道你的向量值在什么结构中，但一般来说，要将向量嵌套在一列中，你可以这样做：

names <- c("A", "B", "C")
vectors <- list(list(1,2,3), list(4,5,6), list(7,8,9))
as.data.frame(cbind(names, vectors))

   names vectors
 1     A 1, 2, 3
 2     B 4, 5, 6
 3     C 7, 8, 9