如何删除R中数据框字符值列的一部分

Question

  [1] NA                         NA                         
  [3] NA                         NA                         
  [5] "kilo130.9"            "kilo5075.69"       
  [7] "kilo465"              "kilo34.8"            
  [9] "kilo607.195"          "kilo1362.7"    

上面是我从R复制粘贴的一个数据帧的列，我运行了下面的代码来删除列中的单词kilo，但它不起作用。我没有得到一个错误，但它没有删除单词kilo。我使用了下面的代码

stopwords = readLines('stopwords.txt') #I put the word kilo in this txt file
x  = df$Dist
x  =  removeWords(x,stopwords)
df$newdist<-x

可能的原因是什么？

Answer 1

removeWords()只会删除与"kilo"完全匹配的单词(没有其他字符)：

x <- c("kilo", "kilo2", "pound")
tm::removeWords(x, "kilo")
#> [1] ""      "kilo2" "pound"

这里有另一个选择：

library("stringr")
x <- c(NA, NA, NA, NA, "kilo130.9", "kilo5075.69", "kilo465", "kilo34.8", "kilo607.195", "kilo1362.7")
str_replace(x, "kilo", "")
#>  [1] NA        NA        NA        NA        "130.9"   "5075.69" "465"    
#>  [8] "34.8"    "607.195" "1362.7"

Answer 2

这是一个使用gsub的基础R解决方案

# Sample data
w <- c(
    NA, NA,
    NA, NA,
    "kilo130.9", "kilo5075.69",
    "kilo465", "kilo34.8",
    "kilo607.195", "kilo1362.7")

# Strings that should be deleted
stopwords <- c("kilo", "something");

sapply(w, function(x)
    x <- gsub(sprintf("(%s)", paste(stopwords, collapse = "|")), "", x));
#       <NA>        <NA>        <NA>        <NA>   kilo130.9 kilo5075.69
#         NA          NA          NA          NA     "130.9"   "5075.69"
#    kilo465    kilo34.8 kilo607.195  kilo1362.7
#      "465"      "34.8"   "607.195"    "1362.7"