R：字符串上的ifelse [英] R: ifelse on string

问题描述

我正在根据另一个变量的字符串条件填充数据框的新变量。我收到以下错误信息：

I am populating a new variable of a dataframe, based on string conditions from another variable. I receive the following error msg:

来源错误==httpWWW.BGDAILYNEWS.COM| Source ==：
只能对数字，逻辑或复杂类型进行操作

我的代码如下：

县< - ifelse（来源=='httpWWW.BGDAILYNEWS.COM'|'WWW.BGDAILYNEWS.COM'，'Warren'，
ifelse（来源=='httpWWW.HCLOCAL.COM'|'WWW.HCLOCAL.COM'，'亨利'，
ifelse（来源=='httpWWW.KENTUCKY.COM'|'WWW.KENTUCKY.COM' ，'Fayette'，
ifelse（来源=='httpWWW.KENTUCKYNEWERA.COM'|'WWW.KENTUCKYNEWERA.COM'，'Christian'）
）））

推荐答案

我建议你将深度嵌套的 ifelse 语句分解为更易于管理的块。

I suggest you break down that deeply nested ifelse statement into more manageable chunks.

但错误告诉你不能像这样使用 | 。 'a'| 'b'因为它是一个逻辑比较而没有意义。而是在％中使用％：

But the error is telling you that you cannot use | like that. 'a' | 'b' doesn't make sense since its a logical comparison. Instead use %in%:

Source %in% c('htpWWW.BGDAILYNEWS.com', 'WWW.BGDAILYNEWS.COM')

我想......如果我理解你在做什么，你会更好地使用多个作业：

I think... If I understand what you're doing, you will be much better off using multiple assignments:

County = vector(mode='character', length=length(Source))
County[County %in% c('htpWWW.BGDAILYNEWS.com', 'WWW.BGDAILYNEWS.COM')] <- 'Warren'
etc.

您还可以使用开关语句这类事情：

You can also use a switch statement for this type of thing:

myfun <- function(x) {
  switch(x,
         'httpWWW.BGDAILYNEWS.COM'='Warren',
         'httpWWW.HCLOCAL.COM'='Henry',
         etc...)
}

然后你想做一个简单的申请（ sapply ）传递来源到 myfun ：

Then you want to do a simple apply (sapply) passing each element in Source to myfun:

County = sapply(Source, myfun)

或者最后，你可以使用因子和等级，但我会将其作为练习留给读者...

Or finally, you can use factors and levels, but I'll leave that as an exercise to the reader...

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