regex - 在R中正确使用gsub/正则表达式？

Question

我有很长的字符串列表，例如此机器可读的示例:

A <- list(c("Biology","Cell Biology","Art","Humanities, Multidisciplinary; Psychology, Experimental","Astronomy & Astrophysics; Physics, Particles & Fields","Economics; Mathematics, Interdisciplinary Applications; Social Sciences, Mathematical Methods","Geriatrics & Gerontology","Gerontology","Management","Operations Research & Management Science","Computer Science, Artificial Intelligence; Computer Science, Information Systems; Engineering, Electrical & Electronic","Economics; Mathematics, Interdisciplinary Applications; Social Sciences, Mathematical Methods; Statistics & Probability"))  

所以看起来像这样:

> A  
[[1]]  
 [1] "Biology"  
 [2] "Cell Biology"  
 [3] "Art"  
 [4] "Humanities, Multidisciplinary; Psychology, Experimental"  
 [5] "Astronomy & Astrophysics; Physics, Particles & Fields"  
 [6] "Economics; Mathematics, Interdisciplinary Applications; Social Sciences, Mathematical Methods"  
 [7] "Geriatrics & Gerontology"  
 [8] "Gerontology"  
 [9] "Management"  
[10] "Operations Research & Management Science"  
[11] "Computer Science, Artificial Intelligence; Computer Science, Information Systems; Engineering, Electrical & Electronic"  
[12] "Economics; Mathematics, Interdisciplinary Applications; Social Sciences, Mathematical Methods; Statistics & Probability"  

我想编辑这些术语并消除重复项，以获得以下结果:

 [1] "Science"  
 [2] "Science"  
 [3] "Arts & Humanities"  
 [4] "Arts & Humanities; Social Sciences"  
 [5] "Science"  
 [6] "Social Sciences; Science"  
 [7] "Science"  
 [8] "Social Sciences"  
 [9] "Social Sciences"  
[10] "Science"  
[11] "Science"  
[12] "Social Sciences; Science"  

到目前为止，我只有这样:

stringedit <- function(A)  
{  
  A <-gsub("Biology", "Science", A)  
  A <-gsub("Cell Biology", "Science", A)  
  A <-gsub("Art", "Arts & Humanities", A)  
  A <-gsub("Humanities, Multidisciplinary", "Arts & Humanities", A)  
  A <-gsub("Psychology, Experimental", "Social Sciences", A)  
  A <-gsub("Astronomy & Astrophysics", "Science", A)  
  A <-gsub("Physics, Particles & Fields", "Science", A)  
  A <-gsub("Economics", "Social Sciences", A)  
  A <-gsub("Mathematics", "Science", A)  
  A <-gsub("Mathematics, Applied", "Science", A)  
  A <-gsub("Mathematics, Interdisciplinary Applications", "Science", A)  
  A <-gsub("Social Sciences, Mathematical Methods", "Social Sciences", A)  
  A <-gsub("Geriatrics & Gerontology", "Science", A)  
  A <-gsub("Gerontology", "Social Sciences", A)  
  A <-gsub("Management", "Social Sciences", A)  
  A <-gsub("Operations Research & Management Science", "Science", A)  
  A <-gsub("Computer Science, Artificial Intelligence", "Science", A)  
  A <-gsub("Computer Science, Information Systems", "Science", A)  
  A <-gsub("Engineering, Electrical & Electronic", "Science", A)  
  A <-gsub("Statistics & Probability", "Science", A)  
}  
B <- lapply(A, stringedit)  

但是它不能正常工作:

> B  
[[1]]  
 [1] "Science"  
 [2] "Cell Science"  
 [3] "Arts & Humanities"  
 [4] "Arts & Humanities; Social Sciences"  
 [5] "Science; Science"  
 [6] "Social Sciences; Science, Interdisciplinary Applications; Social Sciences"  
 [7] "Science"  
 [8] "Social Sciences"  
 [9] "Social Sciences"  
[10] "Operations Research & Social Sciences Science"  
[11] "Computer Science, Arts & Humanitiesificial Intelligence; Science; Science"  
[12] "Social Sciences; Science, Interdisciplinary Applications; Social Sciences; Science"  

如何获得上述正确的输出？
非常感谢您的考虑!

Answer 1

让我从一个例子开始。您有一个字符串“Cell Biology”。第一个替换词A <-gsub("Biology", "Science", A)将其转换为“细胞科学”。然后，该值将不被替换。

由于您不使用正则表达式，因此我宁愿使用某种哈希来进行替换:

myhash <- c( "Science", "Science", "Arts & Humanities", "Arts & Humanities", "Social Sciences", 
  "Science", "Science", "Social Sciences", "Science", "Science", "Science", "Social Sciences", 
  "Science", "Social Sciences", "Social Sciences", "Science", "Science", "Science", "Science", 
  "Science" )

names( myhash ) <- c( "Biology", "Cell Biology", "Art", "Humanities, Multidisciplinary", 
  "Psychology, Experimental", "Astronomy & Astrophysics", "Physics, Particles & Fields", "Economics", 
  "Mathematics", "Mathematics, Applied", "Mathematics, Interdisciplinary Applications", 
  "Social Sciences, Mathematical Methods", "Geriatrics & Gerontology", "Gerontology", "Management",
   "Operations Research & Management Science", "Computer Science, Artificial Intelligence", 
  "Computer Science, Information Systems", "Engineering, Electrical & Electronic", 
  "Statistics & Probability" )

现在，给定诸如“Biology”之类的字符串，您可以快速查找类别:

myhash[ "Biology" ]

我不确定为什么要使用列表而不是字符串向量，因此我将简化您的情况:

A <- c("Biology","Cell Biology","Art",
  "Humanities, Multidisciplinary; Psychology, Experimental",
  "Astronomy & Astrophysics; Physics, Particles & Fields",
  "Economics; Mathematics, Interdisciplinary Applications; Social Sciences, Mathematical Methods",
  "Geriatrics & Gerontology","Gerontology","Management","Operations Research & Management Science",
  "Computer Science, Artificial Intelligence; Computer Science, Information Systems; Engineering, Electrical & Electronic",
  "Economics; Mathematics, Interdisciplinary Applications; Social Sciences, Mathematical Methods; Statistics & Probability")

has查找不适用于复合字符串(包含“;”)。您可以拆分它们，但是可以使用 strsplit。然后，您可以使用 unique避免术语重复，并使用 paste函数将其放回原处。

stringedit <- function( x ) { 
  # first, split into subterms
  a.all <- unlist( strsplit( x, "; *" ) ) ; 
  paste( unique( myhash[ a.all ] ), collapse= "; " ) 
}

unlist( lapply( A, stringedit  ) )

根据需要，结果如下:

[1] "Science"                            "Science"                            "Arts & Humanities"                  "Arts & Humanities; Social Sciences"
[5] "Science"                            "Social Sciences; Science"           "Science"                            "Social Sciences"                   
[9] "Social Sciences"                    "Science"                            "Science"                            "Social Sciences; Science" 

当然，您可以像这样多次调用 *apply:

a.spl <- sapply( A, strsplit, "; *" )
a.spl <- sapply( a.spl, function( x ) myhash[ x ] )
unlist( sapply( a.spl, collapse, "; " )

这并不比以前的代码有效率。

是的，您可以使用正则表达式实现相同的功能，但是首先，它将涉及拆分字符串，然后使用regex之类的 ^Biology$来确保它们将匹配“Biology”而不是“Cell Biology”等。除非您要用于“。* Biology”之类的结构。最后，无论如何，我都必须摆脱重复，而我认为(i)不太冗长(=容易出错)和(ii)不值得付出任何努力。