R中具有多个分类条件的Ifelse [英] Ifelse in R with multiple categorical conditions

问题描述

我有一个数据集 dt.train2 ，其中包含1500个不同的观察值和130个变量。其中之一是语言，可以是英语，法语，阿拉伯语 ...

I have a data set, dt.train2 with 1500 different observations and 130 variables. One of them is languages and it can be english, french, arabic...

我想创建 ifelse 字符串，为英语， 2 1 >对于法语， 3 对于西班牙语和 0 。我不知道该怎么做。

I want to create a ifelse string that gives attributes 1 for english, 2 for french, 3 for spanish and 0 for anything else. I have no idea how to do it.

dt.train2[, language_string := ifelse(language == "english", 
                                      1, 
                                      ifelse(language == "french", 
                                             2, 
                                             ifelse(language == "spanish",3)]

我正在使用它运行有关销售的线性模型。

I'm using this to run linear model about sales.

推荐答案

ifelse（）差不多了，您只需要最后一个 else 结果（还有一对缺少的右括号）。

You're almost there with the ifelse(), you just need the final else result (and a couple missing closing parentheses).

dt.train2[, language_string := ifelse(
  language == "english", 1,
    ifelse(language == "french", 2,
      ifelse(language == "spanish", 3, 0)
    )
  )
]

---

其他几种方法执行以下操作：

---

A couple other ways you could do this:

创建查找表并加入：

# sample data
dt = data.table(language = c("english", "french", "spanish", "arabic", "chinese", "pig latin"))


lookup = data.table(language = c("english", "french", "spanish"),
                    language_string = c(1, 2, 3))

dt2 = merge(dt, lookup, by = "language", all.x = TRUE)
dt2[is.na(language_string), language_string := 0]

上面的查找表方法可能是可伸缩性最好的方法。但是，对于这么少的编码，您也可以只设置每个编码：

The above lookup table method is probably the nicest for scalability. However, for such a small number of encodings, you could also just set each of them:

# start with the default, 0
dt[, language_string := 0 ]
# then do each of the exceptions
dt[lanuage == "english", language_string := 1]
dt[language == "french", language_string := 2]
dt[language == "spanish", language_string := 3]

这篇关于R中具有多个分类条件的Ifelse的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！