循环以基于R中的其他情况创建一个新变量(非常基础) [英] loop to create a new variable based on other cases in R (very basic)

问题描述

我有一个带有三个变量的数据框:ID，group和nominated_ID. 我想知道nominated_ID所属的group.

I have a dataframe with three variables: ID, group, and nominated_ID. I want to know the group that nominated_ID belongs in.

我想对于每种情况，我们采用nominated_ID，找到等于ID的情况，然后将原始情况下的nominated_Group变量设置为等于匹配的情况. (如果没有匹配项，请将其设置为NA)

I'm imagining that for each case, we take nominated_ID, find the case where it is equal to ID, and then set the nominated_Group variable in the original case equal to the group variable in the matched case. (If there is no match, set it to NA)

如果没有循环就可以做到这一点，我不会感到惊讶，因此我对解决方案持开放态度.非常感谢你的帮助.知道我确实在发布之前尝试寻找类似的问题.

I wouldn't be surprised if this can be done without a loop, so I'm open-minded about the solution. Thanks so much for your help. Know that I did try to look for similar questions before posting.

推荐答案

通过直接将结果分配到data.frame中的一列，您可以在不使用cbind的情况下一步实现此目的:

You can achieve this in one step without the use of cbind by directly allocating results to a column in your data.frame:

df$nominated_group <- with(df, group[match(nominated_ID, ID)])
df
  ID group nominated_ID nominated_group
1  9   Odd            9             Odd
2  5   Odd            8            <NA>
3  2  Even            4            Even
4  4  Even            9             Odd
5  3   Odd            2            Even

我使用with作为引用df列的便捷方法，而不必重复编写df$.

I used with as a convenient way of referring to the columns of df without having to repeatedly write df$.

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