R:用先前的值填充缺失的值 [英] R: fill missing value with prior values

问题描述

我有一个看起来像这样的数据框:

I have a dataframe that looks like this:

d <- data.frame(county = c("Abilene", rep(NA, 5), "Cook", rep(NA, 4), "Blah", NA, "Allegheny", rep(NA, 3)))

      county
1    Abilene
2       <NA>
3       <NA>
4       <NA>
5       <NA>
6       <NA>
7       Cook
8       <NA>
9       <NA>
10      <NA>
11      <NA>
12      Blah
13      <NA>
14 Allegheny
15      <NA>
16      <NA>
17      <NA>

我想用先前的非缺失县名的值填写<NA>.换句话说，我想结束这个:

I want to fill in the <NA> with the value of the previous non-missing county name. In other words, I want to end up with this:

  county
1       Abilene
2       Abilene
3       Abilene
4       Abilene
5       Abilene
6       Abilene
7       Cook
8       Cook
9       Cook
10      Cook
11      Cook
12      Blah
13      Blah
14      Allegheny
15      Allegheny
16      Allegheny
17      Allegheny

到目前为止，我一直在遍历d$county中的每个值，使用每个非空县值的名称更新一个临时变量，并重新填充每个单元格.对于大数据帧，这非常慢.我更愿意在dplyr中执行此操作，尽管也可以接受其他任何解决方案.

So far, I have been looping over every value in d$county, updating a temporary variable with the name of every non-empty county value, and refilling each cell. This is very slow with a large dataframe. I would prefer to do this in dplyr, though am open to any other solution as well.

推荐答案

使用tidyr，我们可以使用fill(data, vars):

library(tidyr)
fill(d, county)

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