dplyr:非标准列名(空格、标点符号、以数字开头) [英] dplyr: nonstandard column names (white space, punctuation, starts with numbers)

问题描述

df <- structure(list(`a a` = 1:3, `a b` = 2:4), .Names = c("a a", "a b"
), row.names = c(NA, -3L), class = "data.frame")

数据看起来像

  a a a b
1   1   2
2   2   3
3   3   4

以下调用选择

select(df, 'a a')

给予

Error in abs(ind[ind < 0]) : 
  non-numeric argument to mathematical function

如何使用 select 选择a a"和/或将其重命名为不带空格的名称?我知道以下方法:

How can I select "a a" and/or rename it to something without space using select? I know the following approaches:

1. names(df)[1] <- "a"
2. select(df, a=1)
3. select(df,ends_with("a"))

但是如果我正在处理一个大型数据集，我如何在不知道索引号或类似列名的情况下获得完全匹配?

but if I am working on a large data set, how can I get an exact match without knowing the index numer or similar column names?

推荐答案

您可以使用反引号`select变量.

You may select the variable by using backticks `.

select(df, `a a`)
#   a a
# 1   1
# 2   2
# 3   3

但是，如果您的主要目标是重命名列，则可以使用 plyr 包中的 rename，其中可以同时使用 "" 和 ``.

However, if your main objective is to rename the column, you may use rename in plyr package, in which you can use both "" and ``.

rename(df, replace = c("a a" = "a"))
rename(df, replace = c(`a a` = "a"))

或者在 base R:

names(df)[names(df) == "a a"] <- "a"

有关各种引号使用的更详尽说明，请参阅?Quotes.名称和标识符"部分在此处特别相关:

For a more thorough description on the use of various quotes, see ?Quotes. The 'Names and Identifiers' section is especially relevant here:

可以使用其他 [语法无效] 名称，前提是它们被引用.首选引号是反引号".

other [syntactically invalid] names can be used provided they are quoted. The preferred quote is the backtick".

另见关于有效名称的 ?make.names.

See also ?make.names about valid names.

另请参阅这篇文章关于在<代码>dplyr

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