dplyr的条件突变 [英] conditional mutate by dplyr

问题描述

我想在我的数据集中创建一个新列:i)如果单词本身以"vi"开头，则删除最后一个字符；ii)如果单词本身不以"vi"开头，则删除最后两个字符.我知道如何在R中处理该问题，如下所示:

I want to create a new column in my dataset that: i) drop the last 1 character if the word itself starts with "vi"; and ii) drop the last 2 characters if the word itself does not start with "vi". I know how to work on that in R, like below:

iris$Species <- as.character(iris$Species)
iris$Species_mod <- substr(iris$Species,
                           1,
                           ifelse(grepl('^vi',iris$Species),
                                  nchar(iris$Species)-1,
                                  nchar(iris$Species)-2))

但是我很难在dplyr中破译 mutate ， if_else 和 matches .谁能启发我?谢谢！

But I have a hard time in deciphering the mutate, if_else and matches in dplyr. Can anyone enlighten me? Thanks!

推荐答案

相同的想法，只不过您明确需要将因子转换为字符串

Same idea, except you explicitly need to convert your factor to a string

iris = mutate(iris, Species_mod = substr(Species, 1, nchar(as.character(Species)) - 
    ifelse(grepl('^vi', Species), 1, 2)))

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