R-在不删除NA值的情况下拆分数据帧 [英] R - split data frame without removing NA values

问题描述

如果我有df:

letter    body_part
    a     head
    b     head
    c     NA
    d     NA
    e     left_foot

我想将其拆分为2个dfs ...一个仅包含body_part-"head"，另一个仅包含其他内容.即

And I want to split it into 2 dfs... One with only body_part - "head" and the other with everything else. I.e.

列表<-split(df，df $ body_part =='head')

list <- split(df, df$body_part == 'head')

我可以在不删除NA行的情况下做到这一点吗? (我知道如果我用一个字符串填充NA，就可以做到这一点，但是有一种避免该步骤的方法吗?)

Can I do that without dropping the NA rows? (I know I can do it if I fill the NAs with a string, but is there a way that avoids that step?)

推荐答案

来自?`%in%`:

％in％"永远不会返回"NA"，这使得它在 如果"条件.

That ‘%in%’ never returns ‘NA’ makes it particularly useful in ‘if’ conditions.

# just to show how the `==` comparison compares  
> df$s_col <- df$body_part == 'head'

> split(df, df$body_part %in% 'head')
$`FALSE`
  letter body_part s_col
3      c      <NA>    NA
4      d      <NA>    NA
5      e left_foot FALSE

$`TRUE`
  letter body_part s_col
1      a      head  TRUE
2      b      head  TRUE

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