string R：将数据框行转换为字符向量
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/24492426/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
R: Turning a data frame row into a character vector
提问by nilsole
Short version:
精简版：
I do not understand the behaviour of as.character when trying to convert a single row of a data frame to a character vector.
尝试将数据帧的单行转换为字符向量时，我不明白 as.character 的行为。
> mydf <- data.frame("myvar1"=c("mystring","2"),"myvar2"=c("mystring","3"))
> mydf # nice!
myvar1 myvar2
1 mystring mystring
2 2 3
> as.character(mydf[1,])
[1] "2" "2"
> as.character(as.vector(mydf[1,]) )
[1] "2" "2"
Maybe somebody could give me an explanation for the last 2 output lines and the correct approach? Thanks a lot.
也许有人可以给我解释最后 2 行输出和正确的方法？非常感谢。
Background/Purpose:
背景/目的：
I want to use lre()in order to detect consecutive occurrences of values in a row of a data frame (with columns of different data types).
我想使用lre()它来检测数据框一行中连续出现的值（具有不同数据类型的列）。
Problem: lre()requires a vector, vectors require a definite data type (integer, character, factor, ...). My idea here is to turn the data frame row into a character vector to avoid data loss through conversion.
问题：lre()需要一个向量，向量需要一个明确的数据类型（整数、字符、因子等）。我这里的想法是将数据帧行转换为字符向量，以避免通过转换丢失数据。
采纳答案by csgillespie
Your data frame columns aren't characters they are factors.
您的数据框列不是字符，而是因素。
When you create a data frame the default is that characters are factors. You can see this clearly if you select a column
创建数据框时，默认情况下字符是因子。如果您选择一列，您可以清楚地看到这一点
R> mydf[,1]
[1] mystring 2
Levels: 2 mystring
To avoid this behaviour set the stringsAsFactorsargument to FALSE
为了避免这种行为，将stringsAsFactors参数设置为FALSE
mydf = data.frame("myvar1"=c("mystring", "2"),
"myvar2"=c("mystring", "3"),
stringsAsFactors=FALSE)
You should also look at this question: How to convert a data frame column to numeric type?
您还应该看看这个问题：如何将数据框列转换为数字类型？
回答by coffeinjunky
Try this:
尝试这个：
mydf <- data.frame("myvar1"=c("mystring","2"),"myvar2"=c("mystring","3"), stringsAsFactors=F)
as.character(mydf[1,])
[1] "mystring" "mystring"
Your strings have been coerced into factors, and you have been shown the factor levels.
您的字符串已被强制转换为因子，并且已向您显示因子级别。
