R - 从两个单词的字符串中提取城市名称

Question

我正在使用包含如下城市名称的数据库:

cities <- c("Fairhope 3NE", "Gadsden 19N", "Selma 13 WNW", "Batesville 8 WNW", 
"Elgin 5 S", "Tucson 11 W", "Williams 35 NNW", "Fallbrook 5 NE", 
"Stovepipe Wells 1 SW", "Cortez 8 SE", "La Junta 17 WSW", "Montrose 11 ENE", 
"Everglades City 5 NE", "Sebring 23 SSE", "Brunswick 23 S", "Newton 11 SW", 
"Newton 8 W", "Watkinsville 5 SSE", "Des Moines 17 E", "Champaign 9 SW", 
"Shabbona 5 NNE", "Bedford 5 WNW", "Manhattan 6 SSW", "Oakley 19 SSW", 
"Bowling Green 21 NNE", "Versailles 3 NNW", "Lafayette 13 SE", 
"Monroe 26 N", "Goodridge 12 NNW", "Chillicothe 22 ENE", "Joplin 24 N", 
"Salem 10 W", "Holly Springs 4 N", "Newton 5 ENE", "Asheville 13 S", 
"Asheville 8 SSW", "Durham 11 W", "Jamestown 38 WSW", "Medora 7 E", 
"Northgate 5 ESE", "Harrison 20 SSE", "Lincoln 11 SW", "Lincoln 8 ENE", 
"Whitman 5 ENE", "Las Cruces 20 N", "Los Alamos 13 W", "Socorro 20 N", 
"Mercury 3 SSW", "Coshocton 8 NNE", "Goodwell 2 E", "Stillwater 2 W", 
"Stillwater 5 WNW", "Coos Bay 8 SW", "Corvallis 10 SSW", "Riley 10 WSW", 
"Blackville 3 W", "McClellanville 7 NE", "Aberdeen 35 WNW", "Buffalo 13 ESE", 
"Pierre 24 S", "Sioux Falls 14 NNE", "Crossville 7 NW", "Austin 33 NW", 
"Bronte 11 NNE", "Edinburg 17 NNE", "Monahans 6 ENE", "Muleshoe 19 S", 
"Palestine 6 WNW", "Panther Junction 2 N", "Necedah 5 WNW")

我只想提取城市名称。以下代码适用于某些情况:

gsub( " .*$", "", cities)

但对于具有两个单词名称的城市，它会失败，例如 Stovepipe Wells 1 SW 和 La Junta 17 WSW。

对于这些情况有什么解决方案吗？

Answer 1

您可以删除所有以数字开头的子字符串:

> sub("\\s*\\d.*", "", cities)
 [1] "Fairhope"         "Gadsden"          "Selma"            "Batesville"       "Elgin"            "Tucson"           "Williams"         "Fallbrook"        "Stovepipe Wells" 
[10] "Cortez"           "La Junta"         "Montrose"         "Everglades City"  "Sebring"          "Brunswick"        "Newton"           "Newton"           "Watkinsville"    
[19] "Des Moines"       "Champaign"        "Shabbona"         "Bedford"          "Manhattan"        "Oakley"           "Bowling Green"    "Versailles"       "Lafayette"       
[28] "Monroe"           "Goodridge"        "Chillicothe"      "Joplin"           "Salem"            "Holly Springs"    "Newton"           "Asheville"        "Asheville"       
[37] "Durham"           "Jamestown"        "Medora"           "Northgate"        "Harrison"         "Lincoln"          "Lincoln"          "Whitman"          "Las Cruces"      
[46] "Los Alamos"       "Socorro"          "Mercury"          "Coshocton"        "Goodwell"         "Stillwater"       "Stillwater"       "Coos Bay"         "Corvallis"       
[55] "Riley"            "Blackville"       "McClellanville"   "Aberdeen"         "Buffalo"          "Pierre"           "Sioux Falls"      "Crossville"       "Austin"          
[64] "Bronte"           "Edinburg"         "Monahans"         "Muleshoe"         "Palestine"        "Panther Junction" "Necedah"         
> 

这里，

• \\s* - 匹配 0+ 个空格
• \\d - 一个数字
• .* - 字符串的其余部分。

参见 regex demo . sub 只执行一个匹配和替换操作。