将具有交替缺失值的两个字符串列合并为一个 [英] Coalesce two string columns with alternating missing values to one

问题描述

我有一个包含两列a"和b"的数据框，其中包含交替的缺失值(NA)

I have a data frame with two columns "a" and "b" with alternating missing values (NA)

a      b
dog    <NA>
mouse  <NA>
<NA>   cat
bird   <NA>

我想将它们合并"/组合到一个看起来像这样的新列 c，即每行中的非 NA 元素被选中:

I want to "merge" / combine them to a new column c that looks like this, i.e. the non-NA element in each row is selected:

c
dog
mouse
cat
bird

我尝试了 merge 和 join，但都没有达到我想要的效果.也许是因为我没有要合并的 ID?对于整数，我会绕过这个并添加两列，但在我的情况下如何?

I tried merge and join, but neither worked as I wanted. Maybe because I do not have an id with which to merge? For integers I would just circumvent this and add both columns, but how in my case?

推荐答案

你可以试试pmax

df$c <- pmax(df$a, df$b)
df
#       a    b     c
# 1   dog <NA>   dog
# 2 mouse <NA> mouse
# 3  <NA>  cat   cat
# 4  bird <NA>  bird

...或 ifelse:

df$c <- ifelse(is.na(df$a), df$b, df$a)

对于两列以上情况的更通用解决方案，您可以在 R 中找到几种实现合并的方法 这里.

For more general solutions in cases with more than two columns, you find several ways to implement coalesce in R here.

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