如何将向量分组为向量列表? [英] How to group a vector into a list of vectors?

问题描述

我有一些看起来像这样的数据(例如假数据):

dressId 颜色6黄色9红10绿色10紫10黄色12紫12红

其中颜色是一个因子向量.不保证所有可能的因子水平都实际出现在数据中(例如，蓝色"颜色也可能是其中的一个水平).

我需要一个向量列表，用于对每件衣服的可用颜色进行分组:

<代码>[[1]]黄色的[[2]]红色的[[3]]绿色 紫色 黄色[[4]]紫红色

保留衣服的 ID 会很好(例如，此列表是第二列而 ID 是第一列的数据框)，但不是必需的.

我写了一个循环，它遍历数据帧行，虽然下一个 ID 相同，但它将颜色添加到向量中.(我确定数据是按 ID 排序的).当第一列中的 ID 发生变化时，它会将向量添加到列表中:

result <- NULL同时(等等){一些创建称为颜色"的向量的代码结果[[dressCounter]] <- 颜色着装计数器 <- 着装计数器 + 1}

在努力使所有必要的计数变量正确后，我沮丧地发现它不起作用.第一次，colors 是

[1] 黄色层次:绿黄紫红蓝

它被强制转换为一个整数，所以 result 变成 2.

在第二次循环中，colors 只包含红色，result 变成了一个简单的整数向量，[1] 2 4.

在第三次重复中，colors 现在是一个向量，

[1] 绿色 紫色 黄色层次:绿黄紫红蓝

我得到

result[[3]] <- 颜色

<块引用>

结果错误[[3]] <-颜色:
提供的元素多于替换的元素

我做错了什么?有没有办法初始化 result 这样它就不会被转换成数字向量，而是变成一个向量列表?

此外，除了自己动手"之外，还有其他方法可以完成整个事情吗?

解决方案

split.data.frame 是一个很好的组织方式；然后提取颜色分量.

d <- data.frame(dressId=c(6,9,10,10,10,12,12),颜色=因子(c(黄色"，红色"，绿色"，紫色"，黄色"，"紫色","红色"),水平= c(红色"，橙色"，黄色"，绿色"、蓝色"、紫色")))

我认为你想要的版本实际上是这样的:

ss <- split.data.frame(d,d$dressId)

通过提取颜色分量，您可以获得更像您请求的列表的内容:

lapply(ss,"[[","color")

I have some data which looks like this (fake data for example's sake):

dressId        color 
6              yellow 
9              red
10             green 
10             purple 
10             yellow 
12             purple 
12             red 

where color is a factor vector. It is not guaranteed that all possible levels of the factor actually appear in the data (e.g. the color "blue" could also be one of the levels).

I need a list of vectors which groups the available colors of each dress:

[[1]]
yellow  

[[2]] 
red    

[[3]] 
green purple yellow 

[[4]] 
purple red 

Preserving the IDs of the dresses would be nice (e.g. a dataframe where this list is the second column and the IDs are the first), but not necessary.

I wrote a loop which goes through the dataframe row for row, and while the next ID is the same, it adds the color to a vector. (I am sure that the data is sorted by ID). When the ID in the first column changes, it adds the vector to a list:

result <- NULL 
while(blah blah) 
{
    some code which creates the vector called "colors" 
    result[[dressCounter]] <- colors 
    dressCounter <- dressCounter + 1
}

After wrestling with getting all the necessary counting variables correct, I found out to my dismay that it doesn't work. The first time, colors is

[1] yellow
Levels: green yellow purple red blue

and it gets coerced into an integer, so result becomes 2.

In the second loop repetition, colors only contains red, and result becomes a simple integer vector, [1] 2 4.

In the third repetition, colors is a vector now,

[1] green  purple yellow
Levels: green yellow purple red blue 

and I get

result[[3]] <- colors

Error in result[[3]] <- colors :
more elements supplied than there are to replace

What am I doing wrong? Is there a way to initialize result so it doesn't get converted into a numeric vector, but becomes a list of vectors?

Also, is there another way to do the whole thing than "roll my own"?

解决方案

split.data.frame is a good way to organize this; then extract the color component.

d <- data.frame(dressId=c(6,9,10,10,10,12,12),
               color=factor(c("yellow","red","green",
                              "purple","yellow",
                              "purple","red"),
                 levels=c("red","orange","yellow",
                          "green","blue","purple")))

I think the version you want is actually this:

ss <- split.data.frame(d,d$dressId)

You can get something more like the list you requested by extracting the color component:

lapply(ss,"[[","color")

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