R中的字符串重排

Question

我有一长串城市名称及其省份名称。这是我的部分数据列表

data <- c('Ranchi_Capital_State_Jharkhand', 'Bokaro_State_Jharkhand', 'Tata Nagar_State_Jharkhand', 'Ramgarh_State_Jharkhand',
      'Pune_State_Maharashtra', 'Mumbai_Capital_State_Maharashtra', 'Nagpur_State_Maharashtra')

我想把状态排在第一位，像这样State_Jharkhand_Bokaro。如果城市是首都，则 State_Jharkhand_Capital_Ranchi。另请注意，城市名称或州名称可能只有一个字符串或多个字符串（例如 Tata Nagar）。

最有效的方法是什么（不使用任何循环）？

Answer 1

这并没有真正使用太多正则表达式，而是主要基于信息的预期位置。用“_”拆分字符串，然后根据需要重新排序：

data
# [1] "Ranchi_Capital_State_Jharkhand"   "Bokaro_State_Jharkhand"          
# [3] "Tata Nagar_State_Jharkhand"       "Ramgarh_State_Jharkhand"         
# [5] "Pune_State_Maharashtra"           "Mumbai_Capital_State_Maharashtra"
# [7] "Nagpur_State_Maharashtra"  

A <- strsplit(data, "_", TRUE)
sapply(A, function(x) {
  if (length(x) == 3) {
    paste(x[c(2, 3, 1)], collapse = "_")
  } else if (length(x) == 4) {
    paste(x[c(3, 4, 2, 1)], collapse = "_")
  } else {
    stop("unexpected length")
  }
})
# [1] "State_Jharkhand_Capital_Ranchi"   "State_Jharkhand_Bokaro"          
# [3] "State_Jharkhand_Tata Nagar"       "State_Jharkhand_Ramgarh"         
# [5] "State_Maharashtra_Pune"           "State_Maharashtra_Capital_Mumbai"
# [7] "State_Maharashtra_Nagpur"

我不知道使用 sapply 是否违反了您对 "without using any loop" 的要求。

Answer 2

您可以使用下面的 gsub 函数。

> data <- c('Ranchi_Capital_State_Jharkhand', 'Bokaro_State_Jharkhand', 'Tata Nagar_State_Jharkhand', 'Ramgarh_State_Jharkhand',
+           'Pune_State_Maharashtra', 'Mumbai_Capital_State_Maharashtra', 'Nagpur_State_Maharashtra')
> gsub("^(?:(.*?)(_Capital))?(.*?)_(State.*)", "\4\2_\1\3", data)
[1] "State_Jharkhand_Capital_Ranchi"   "State_Jharkhand_Bokaro"          
[3] "State_Jharkhand_Tata Nagar"       "State_Jharkhand_Ramgarh"         
[5] "State_Maharashtra_Pune"           "State_Maharashtra_Capital_Mumbai"
[7] "State_Maharashtra_Nagpur"

DEMO

R中的字符串重排

String rearrangment in R

regex

r

string

gsub

strsplit