字符串拆分和条件粘贴

Question

我正在处理如下数据框

        id            Comments
        1             The apple fell far from the mango tree
        2             I was born under a mango tree and a wandering star      
        3             Mules are made for packing and Mangoes for eating

我对 mango 这个词之前的 4 个词和之后的 4 个词感兴趣，包括 mango 这个词。

最终数据集将如下所示。

        id            Comments
        1             far from the mango tree
        2             born under a mango tree and a      
        3             for packing and Mangoes for eating

这是测试可重现的数据集

df <- read.table(text="Id,Comment
 1,The apple fell far from the mango tree
                 2,I was born under a mango tree and a wandering star      
                 3,Mules are made for packing and Mangoes for eating", header=T, sep=",")

关于这个非常适用的任何见解

Answer 1

我使用了非常好的 stringi 包和正则表达式技术：

library(stringi)
apply(df,1, function(myrow){
   stri_match_all_regex(myrow[2], "(\p{L}+\p{Z}){0,3}(mango\p{L}*|Mango\p{L}*)(\p{Z}\p{L}+){0,3}")[[1]][1,1]
   })

所以我在 mango ((\p{L}+\p{Z}){0,3}) 之前得到 0 到 3 个单词，在那个 mango 或 Mango 后面有额外的字母 ((mango\p{L}*|Mango\p{L}*)) 之后又从0 到 3 个字 ((\p{Z}\p{L}+){0,3})

其中 \p{Z} 是一个空格，\p{L} 是一个字母。

Answer 2

这似乎有效：

sapply(
  strsplit(as.character(df$Comment), " "),
  function(x){
    w = grep("[m|M]ango", x)[1]
    paste(x[ seq(max(1,w-3), min(length(x),w+3)) ], collapse=" ") 
  }
)
# [1] "far from the mango tree"           
# [2] "born under a mango tree and a"     
# [3] "for packing and Mangoes for eating"

grep(...)[1]表示只使用第一个芒果匹配。

字符串拆分和条件粘贴

string split and conditional paste

string

r

gsub

stringr

grepl