如何遍历数据框列表以在 R 中设置列名？答案

【问题标题】：How to loop through through list of data frames to set column names in R?如何遍历数据框列表以在 R 中设置列名？
【发布时间】：2020-12-16 22:29:48
【问题描述】：

我有大量数据框，我想根据第一列和第四行的条件设置列名。请在下面找到我的示例数据：

sample_data<-data.frame(a= c("\"\"","This","Week","1","2",  "3",   "4",  "5", "6" ),b=c("\"\""      , "Last"   ,   "Week"  , "(1)"    ,       "(2)"   ,       "(3)"     ,       "(4)"     ,           "(5)"   ,      "(6)"   ) ,c=c("\"\"" , "End","2008"  , "<1>",   "<2>",  "<3>", "<4>", "<5>", "<6>"  ) ,
                            d=c(""   ,    "Name"   ,   "" ,      "Tiger Woods" ,  "Sergio Garcia" ,"Phil Mickelson" ,"Padraig Harrington", "Vijay Singh" ,"Robert Karlsson") ,e=c("", "Country" ,  "",       "United States" ,"Spain",         "United States" , "Ireland" ,           "Fiji" , "Sweden"     ),
                            f=c("" ,  "Average" ,  "Points" ,"11.664"    ,    "7.992"    ,     "6.871"  ,        "6.832"   ,           "6.631"   ,    "5.017"  ),f=c("", "Total" ,"Points","466.573" ,"415.591" ,"336.674", "348.431",  "358.071", "265.906" ))



another_data<-data.frame(a=c("\"\"","Last", "Week" ,"\"\"","(50)", "(55)","(51)","(52)"),b=c("\"\"" ,"End", "2011","\"\"", "<148>","<70>","<49>","<51>"),c=c("","Name", "\"\"" ,"" ,"Kyle Stanley" , "Kevin Na" ,"Gonzalo Fdez-Castano" ,"Ryo Ishikawa") ,
                              d=c("","State","\"\"","\"\"", "United States","United States" ,"Spain" ,"Japan"),e=c("\"\"" ,"Country" ,"\"\"","\"\"","United States", "United States" ,"Spain","Japan"),f=c("\"\"","Average" ,"Points" ,"","2.694" ,"2.560","2.544" ,"2.539")) 
     
               
list_df<-list(sample_data,another_data)


list_df
[[1]]
     a    b    c                  d             e       f     f.1
1   ""   ""   ""                                                 
2 This Last  End               Name       Country Average   Total
3 Week Week 2008                                   Points  Points
4    1  (1)  <1>        Tiger Woods United States  11.664 466.573
5    2  (2)  <2>      Sergio Garcia         Spain   7.992 415.591
6    3  (3)  <3>     Phil Mickelson United States   6.871 336.674
7    4  (4)  <4> Padraig Harrington       Ireland   6.832 348.431
8    5  (5)  <5>        Vijay Singh          Fiji   6.631 358.071
9    6  (6)  <6>    Robert Karlsson        Sweden   5.017 265.906

[[2]]
     a     b                    c             d             e       f
1   ""    ""                                               ""      ""
2 Last   End                 Name         State       Country Average
3 Week  2011                   ""            ""            ""  Points
4   ""    ""                                 ""            ""        
5 (50) <148>         Kyle Stanley United States United States   2.694
6 (55)  <70>             Kevin Na United States United States   2.560
7 (51)  <49> Gonzalo Fdez-Castano         Spain         Spain   2.544
8 (52)  <51>         Ryo Ishikawa         Japan         Japan   2.539

所以我想做的是检查第四行是否包含""。如果是这样，请将数据框第四行到第一行之间的所有内容合并。另一方面，如果第四行不包含""，则合并第三行到数据框第一行之间的所有内容。

这是我的试验：

for (index in 1:length(list_df))
{

  if(list_df[[index]][4,1]=="")
    {
      list_df[[index]]<-setNames(as.data.frame(list_df[[index]][-(1:4), ]),
                                                sapply(as.data.frame(list_df[[index]][1:4, ]), paste, collapse = ""))
    }
  else if(list_df[[index]][4,1]!="")
  {
    list_df[[index]]<-setNames(as.data.frame(list_df[[index]][-(1:3), ]),
                                sapply(as.data.frame(list_df[[index]][1:3, ]), paste, collapse = ""))
  }
  {
    return(list_df)
  }

}

但这并没有给我想要的输出。只考虑第一个条件，不考虑第二个条件。

这是我得到的输出：

list_df

   [[1]]
      ThisWeek LastWeek End2008               Name       Country AveragePoints TotalPoints
    4        1      (1)     <1>        Tiger Woods United States        11.664     466.573
    5        2      (2)     <2>      Sergio Garcia         Spain         7.992     415.591
    6        3      (3)     <3>     Phil Mickelson United States         6.871     336.674
    7        4      (4)     <4> Padraig Harrington       Ireland         6.832     348.431
    8        5      (5)     <5>        Vijay Singh          Fiji         6.631     358.071
    9        6      (6)     <6>    Robert Karlsson        Sweden         5.017     265.906
    
    [[2]]
         a     b                    c             d             e       f
    1                                                                    
    2 Last   End                 Name       Country       Country Average
    3 Week  2011                                                   Points
    4                                                                    
    5 (50) <148>         Kyle Stanley United States United States   2.694
    6 (55)  <70>             Kevin Na United States United States   2.560
    7 (51)  <49> Gonzalo Fdez-Castano         Spain         Spain   2.544
    8 (52)  <51>         Ryo Ishikawa         Japan         Japan   2.539

但是，所需的输出如下：

list_df

[[1]]
          ThisWeek LastWeek End2008               Name       Country AveragePoints TotalPoints
        4        1      (1)     <1>        Tiger Woods United States        11.664     466.573
        5        2      (2)     <2>      Sergio Garcia         Spain         7.992     415.591
        6        3      (3)     <3>     Phil Mickelson United States         6.871     336.674
        7        4      (4)     <4> Padraig Harrington       Ireland         6.832     348.431
        8        5      (5)     <5>        Vijay Singh          Fiji         6.631     358.071
        9        6      (6)     <6>    Robert Karlsson        Sweden         5.017     265.906

[[2]]
   LastWeek   End2011         Name                  State        Country  AveragePoints
5    (50)     <148>         Kyle Stanley           United States United States   2.694
6    (55)      <70>         Kevin Na               United States United States   2.560
7    (51)      <49>         Gonzalo Fdez-Castano   Spain         Spain           2.544
8    (52)      <51>         Ryo Ishikawa           Japan         Japan           2.539

我对此感到非常困惑。我不知道为什么其中一个条件被忽略了。谁能帮我解决这个问题？

【问题讨论】：

您能否展示给定示例的预期输出？
我已经更新了我的问题。我现在已经包含了所需的输出。提前致谢。

标签： r list for-loop merge concat

【解决方案1】：

通常使用lapply 迭代列表很容易。你可以试试：

lapply(list_df, function(x) {
  if (x[4, 1] == '""') {
    names(x) = gsub('"', '', trimws(sapply(x[1:4, ], paste, collapse = "")))
    x[-c(1:4), ]
  }
  else {
    names(x) = gsub('"', '', trimws(sapply(x[1:3, ], paste, collapse = "")))
    x[-c(1:3), ]
  }
})

#[[1]]
#  ThisWeek LastWeek End2008               Name       Country AveragePoints TotalPoints
#4        1      (1)     <1>        Tiger Woods United States        11.664     466.573
#5        2      (2)     <2>      Sergio Garcia         Spain         7.992     415.591
#6        3      (3)     <3>     Phil Mickelson United States         6.871     336.674
#7        4      (4)     <4> Padraig Harrington       Ireland         6.832     348.431
#8        5      (5)     <5>        Vijay Singh          Fiji         6.631     358.071
#9        6      (6)     <6>    Robert Karlsson        Sweden         5.017     265.906

#[[2]]
#  LastWeek End2011                 Name         State       Country AveragePoints
#5     (50)   <148>         Kyle Stanley United States United States         2.694
#6     (55)    <70>             Kevin Na United States United States         2.560
#7     (51)    <49> Gonzalo Fdez-Castano         Spain         Spain         2.544
#8     (52)    <51>         Ryo Ishikawa         Japan         Japan         2.539

就您的for 循环而言，它不起作用的主要原因是您正在寻找错误的字符。 [4, 1] 的值是 "" 而不是空字符串（检查 another_data[4, 1] == '' 与 another_data[4, 1] == '""')。如果你改变它，你应该得到所需的输出。但是，我在您的 for 循环中做了一些额外的更改。

删除了额外的 else if 条件，因为它不需要。
在我的回答中添加了gsub，以从列名中删除引号
return(list_df) 没有意义，因为我们已经在 for 循环中更改了 list_df，因此将其删除。

for (index in 1:length(list_df)) {
  if(list_df[[index]][4,1] == '""') {
    list_df[[index]]<-setNames(as.data.frame(list_df[[index]][-(1:4), ]),
                    gsub('"', '',sapply(as.data.frame(list_df[[index]][1:4, ]), 
                 paste, collapse = "")))
  }
  else{
    list_df[[index]]<-setNames(as.data.frame(list_df[[index]][-(1:3), ]),
                  gsub('"', '', sapply(as.data.frame(list_df[[index]][1:3, ]), 
                  paste, collapse = "")))
  }
}

【讨论】：

您好 Ronak，当我尝试在更大范围内实现此登录时，我一遍又一遍地收到此错误。 '名称错误（对象）
也许这些数据的结构与我们这里的不同？我在想这可能是由于NA's 但NAs 在这里应该无关紧要。尝试对单个文件 list_df[[1]]、list_df[[2]] 运行它，看看它们是否返回错误。拥有大量数据不太可能是造成这种情况的原因。
感谢您的帮助。我想我现在发现了问题。其中一个数据框有一个导致问题的空列。这意味着我试图将列名分配给一个空列，结果它抛出了那个错误。现在我正在尝试删除那个空列，我猜它应该可以工作。