6

我有一长串字符串，例如这个机器可读的例子： 

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"))

所以它看起来像这样： 

> 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此结果： 

 [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，我只得到了这个： 

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"

我怎样才能获得上述正确的输出？
非常感谢您的考虑！

4

3 回答 3

5

我发现使用两列data.frame作为查找最容易，一列用于课程名称，一列用于类别。这是一个例子：

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

然后，假设A作为您的问题中的列表：

sapply(strsplit(unlist(A), "; "), 
       function(x) 
         paste(unique(course.categories[match(x, course.categories[["Course"]]),
                                        "Category"]), 
               collapse = "; "))
#  [1] "Science"                            "Science"                           
#  [3] "Arts & Humanities"                  "Arts & Humanities; Social Sciences"
#  [5] "Science"                            "Social Sciences; Science"          
#  [7] "Science"                            "Social Sciences"                   
#  [9] "Social Sciences"                    "Science"                           
# [11] "Science"                            "Social Sciences; Science"

match将值A与数据集中的课程名称相匹配，course.categories并说明匹配发生在哪些行上；这用于提取课程所属的类别。然后，unique确保我们只有每个类别中的一个。paste把事情重新组合在一起。

于 2012-10-22T12:18:24.377 回答
4

让我从一个例子开始。你有一个字符串“细胞生物学”。第一个替换，A <-gsub("Biology", "Science", A)将它变成“细胞科学”。然后不会被替换。

由于您不使用正则表达式，我宁愿使用一种哈希来进行替换：

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，给定一个字符串，例如“Biology”，您可以快速查找您的类别：

myhash[ "Biology" ]

我不确定您为什么要使用列表而不是字符串向量，因此我将简化一下您的情况：

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，但是使用strsplit. 然后，您可以使用unique来避免术语重复，并使用该paste功能将其重新组合在一起。

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

unlist( lapply( A, stringedit  ) )

这是所需的结果：

[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，你可以*apply这样调用几次：

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

这并不比前面的代码效率更高或更低。

是的，你可以用正则表达式实现同样的效果，但首先，它无论如何都会涉及拆分字符串，然后使用正则表达式^Biology$来确保它们匹配“生物学”而不是“细胞生物学”等。除非你想去像“.* Biology”这样的结构。最后，无论如何，您都必须摆脱重复项，而这一切都将是，在我看来（i）不那么冗长（= 更容易出错）和（ii）不值得付出努力。

于 2012-10-22T11:03:48.263 回答
2

以及如何使用switch？

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

a <- unlist(lapply(A, strsplit, split = " *; *"), recursive = FALSE)
a1 <- lapply(a, function(x) unique(sapply(x, science.category)))
sapply(a1, paste, collapse = "; ")

当然，只要您有适当的字符串作为switch参数，这将起作用。一个不匹配，你会以NA. 对于一些高级用法，您应该编写自己的包装器以使用grep-family 函数，甚至agrep（小心处理）。

于 2012-10-22T11:48:08.473 回答