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

问题描述

我有一个数据集 dt.train2 有 1500 个不同的观察值和 130 个变量.其中之一是languages，它可以是english、french、arabic...

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...

我想创建一个 ifelse 字符串，它为 english 提供属性 1，为 提供 2法语，3 用于spanish 和0 用于其他任何内容.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)]

我正在使用它来运行关于销售的线性模型.

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

推荐答案

ifelse() 就快到了，你只需要最终的 else 结果(和一对缺少右括号).

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)
    )
  )
]

<小时>

您可以通过其他几种方式来做到这一点:

---

A couple other ways you could do this:

制作查找表并加入:

# 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]

上述查找表方法可能是可扩展性最好的方法.但是，对于如此少量的编码，您也可以只设置它们中的每一个:

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]

这篇关于具有多个分类条件的 R 中的 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！