使用cbind从两个向量创建数据帧 [英] Creating a data frame from two vectors using cbind

问题描述

考虑以下R代码。

> x = cbind(c(10, 20), c("[]", "[]"), c("[[1,2]]","[[1,3]]"))
> x
     [,1] [,2] [,3]     
[1,] "10" "[]" "[[1,2]]"
[2,] "20" "[]" "[[1,3]]"

同样

> x = rbind(c(10, "[]", "[[1,2]]"), c(20, "[]", "[[1,3]]"))
> x
     [,1] [,2] [,3]     
[1,] "10" "[]" "[[1,2]]"
[2,] "20" "[]" "[[1,3]]"

现在，我不要将整数 10 和 20 转换为字符串。
如果没有任何这样的转换，我该如何执行此操作？我的
课程也想知道为什么会发生这种转换。我查看了
code> cbind 帮助，并尝试使用Google搜索，但没有运气找到
解决方案。我也相信在某些情况下。 R将字符串转换为
因子，而且我也不希望这种情况发生，尽管这里似乎没有
。

Now, I don't want the integers 10 and 20 to be converted to strings. How can I perform this operation without any such conversion? I would of course also like to know why this conversion happens. I looked at the cbind help and also tried Googling, but had no luck finding a solution. I also believe that in some cases. R converts strings to factors, and I don't want that to happen either, though it doesn't seem to be happening here.

推荐答案

向量和矩阵只能是单个类型，而 cbind 和 rbind

Vectors and matrices can only be of a single type and cbind and rbind on vectors will give matrices. In these cases, the numeric values will be promoted to character values since that type will hold all the values.

（请注意，在您的 rbind 示例，促销发生在 c 调用中：

(Note that in your rbind example, the promotion happens within the c call:

> c(10, "[]", "[[1,2]]")
[1] "10"      "[]"      "[[1,2]]"

如果你想要一个矩形结构，列可以是不同的类型，你想要一个数据。框架。以下任何一项都可以让您满意：

If you want a rectangular structure where the columns can be different types, you want a data.frame. Any of the following should get you what you want:

> x = data.frame(v1=c(10, 20), v2=c("[]", "[]"), v3=c("[[1,2]]","[[1,3]]"))
> x
  v1 v2      v3
1 10 [] [[1,2]]
2 20 [] [[1,3]]
> str(x)
'data.frame':   2 obs. of  3 variables:
 $ v1: num  10 20
 $ v2: Factor w/ 1 level "[]": 1 1
 $ v3: Factor w/ 2 levels "[[1,2]]","[[1,3]]": 1 2

或（具体使用 data.frame 版本的 cbind ）

> x = cbind.data.frame(c(10, 20), c("[]", "[]"), c("[[1,2]]","[[1,3]]"))
> x
  c(10, 20) c("[]", "[]") c("[[1,2]]", "[[1,3]]")
1        10            []                 [[1,2]]
2        20            []                 [[1,3]]
> str(x)
'data.frame':   2 obs. of  3 variables:
 $ c(10, 20)              : num  10 20
 $ c("[]", "[]")          : Factor w/ 1 level "[]": 1 1
 $ c("[[1,2]]", "[[1,3]]"): Factor w/ 2 levels "[[1,2]]","[[1,3]]": 1 2

或（使用 cbind ，但是将第一个 data.frame ，以便它作为data.frames执行）：

or (using cbind, but making the first a data.frame so that it combines as data.frames do):

> x = cbind(data.frame(c(10, 20)), c("[]", "[]"), c("[[1,2]]","[[1,3]]"))
> x
  c.10..20. c("[]", "[]") c("[[1,2]]", "[[1,3]]")
1        10            []                 [[1,2]]
2        20            []                 [[1,3]]
> str(x)
'data.frame':   2 obs. of  3 variables:
 $ c.10..20.              : num  10 20
 $ c("[]", "[]")          : Factor w/ 1 level "[]": 1 1
 $ c("[[1,2]]", "[[1,3]]"): Factor w/ 2 levels "[[1,2]]","[[1,3]]": 1 2

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