r - 语法无效名称的后果

Question

read.table 系列(read.table、read.csv、read.delim 等) 的参数 check.names 具有以下解释:

logical. If TRUE then the names of the variables in the data frame are checked to ensure that they are syntactically valid variable names. If necessary they are adjusted (by make.names) so that they are, and also to ensure that there are no duplicates.

假设我加载了一个包含语法无效的列名的数据框。除了必须使用 ` 字符按名称访问特定列之外，还有其他后果吗？

Answer 1

查看 help(make.names) 以了解它在做什么以及为什么。

A syntactically valid name consists of letters, numbers and the dot or underline characters and starts with a letter or the dot not followed by a number. Names such as ".2way" are not valid, and neither are the reserved words.

The definition of a letter depends on the current locale, but only ASCII digits are considered to be digits.

The character "X" is prepended if necessary. All invalid characters are translated to ".". A missing value is translated to "NA". Names which match R keywords have a dot appended to them. Duplicated values are altered by make.unique.

最让你困惑的是空白列名(df$`` 给出错误)和重复的列名(df$val 将返回第一个仅val 列结果)。

除此之外，如果您将此 data.frame 传递给需要具有有效名称的 data.frame 的函数，您可能会收到错误，并且可能会收到难以检测的静默错误。