如何修剪前导和尾随空格? [英] How to trim leading and trailing whitespace?

问题描述

我在data.frame中的前导和尾随空白时遇到了麻烦. 例如，我想根据特定条件查看data.frame中的特定row:

I am having some troubles with leading and trailing whitespace in a data.frame. Eg I like to take a look at a specific row in a data.frame based on a certain condition:

> myDummy[myDummy$country == c("Austria"),c(1,2,3:7,19)] 

[1] codeHelper     country        dummyLI    dummyLMI       dummyUMI       
[6] dummyHInonOECD dummyHIOECD    dummyOECD      
<0 rows> (or 0-length row.names)

我想知道为什么我没有得到预期的产出，因为我的data.frame显然存在奥地利这个国家.在查看了我的代码历史记录并尝试找出出了什么问题之后，我尝试了:

I was wondering why I didn't get the expected output since the country Austria obviously existed in my data.frame. After looking through my code history and trying to figure out what went wrong I tried:

> myDummy[myDummy$country == c("Austria "),c(1,2,3:7,19)]
   codeHelper  country dummyLI dummyLMI dummyUMI dummyHInonOECD dummyHIOECD
18        AUT Austria        0        0        0              0           1
   dummyOECD
18         1

我在命令中所做的所有更改都是在奥地利之后添加了一个空白.

All I have changed in the command is an additional whitespace after Austria.

显然还会出现其他烦人的问题.例如，当我想根据国家/地区"列合并两个框架时.一个data.frame使用"Austria "，而另一帧使用"Austria".匹配无效.

Further annoying problems obviously arise. Eg when I like to merge two frames based on the country column. One data.frame uses "Austria " while the other frame has "Austria". The matching doesn't work.

1. 有没有一种很好的方法可以在屏幕上显示"空白，以便使我意识到问题所在?
2. 我可以删除R中的前导空格和尾随空格吗?

到目前为止，我曾经写过一个简单的Perl脚本，该脚本删除了空格，但是如果我能以某种方式在R中完成它会很好.

So far I used to write a simple Perl script which removes the whitespace but it would be nice if I can somehow do it inside R.

推荐答案

可能最好的方法是在读取数据文件时处理尾随空格.如果使用read.csv或read.table，则可以设置参数strip.white=TRUE.

Probably the best way is to handle the trailing whitespaces when you read your data file. If you use read.csv or read.table you can set the parameterstrip.white=TRUE.

如果以后要清理字符串，则可以使用以下功能之一:

If you want to clean strings afterwards you could use one of these functions:

# returns string w/o leading whitespace
trim.leading <- function (x)  sub("^\\s+", "", x)

# returns string w/o trailing whitespace
trim.trailing <- function (x) sub("\\s+$", "", x)

# returns string w/o leading or trailing whitespace
trim <- function (x) gsub("^\\s+|\\s+$", "", x)

要在myDummy$country上使用以下功能之一:

To use one of these functions on myDummy$country:

 myDummy$country <- trim(myDummy$country)

---

要显示"空白，您可以使用:

---

To 'show' the whitespace you could use:

 paste(myDummy$country)

这将为您显示带引号()括起来的字符串，使空格更容易发现.

which will show you the strings surrounded by quotation marks (") making whitespaces easier to spot.

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