r - 为坐标选择正确的正则表达式

Question

我有各种格式的坐标，并尝试获得或多或少通用的转换例程。

为此，我尝试使用正则表达式解析字符串的各个元素，并尝试通过字符串中出现的索引来获取度、分和秒的各个信息。

对于某些人来说它有效......但不适用于所有人。我非常确信我的问题与我对正则表达式的有限理解密切相关。

因此问题是:谁对正则表达式模式有更好的理解并且可以提供帮助？

我尝试编译一小段代码来演示该问题。运行下面的示例显示我得到了前四个和最后三个坐标的三个分量。其余部分 - 中间 - 仅提供 2 个组件......

coords = c("-53°30''30.54'",
       "s55°30' 30.54",
       "55°30'30.54n",
       "0°1 0.5S",
       "-0°30'30''s",
       "S55 30 30",
       "-55°30'30''",
       "-55° 30' 30''",
       "-55°   30'   30",
       "-55 sometimes with text rests 30 30''",
       "55°30'30,54S",
       "S55° 30' 30,54",
       "-55° 30' 30.54''"
       )

for (i in 1:length (coords)) {
    pattern   <- gregexpr ("[0-9.]+", coords [i])
    print (as.character (unique (unlist (regmatches (coords [i], pattern)))))
}


<Output>
[1] "53"    "30"    "30.54"
[1] "55"    "30"    "30.54"
[1] "55"    "30"    "30.54"
[1] "0"   "1"   "0.5"
[1] "0"  "30"
[1] "55" "30"
[1] "55" "30"
[1] "55" "30"
[1] "55" "30"
[1] "55" "30"
[1] "55" "30" "54"
[1] "55" "30" "54"
[1] "55"    "30"    "30.54"

下面的正则表达式是一个令人印象深刻的怪物;-) 然而，当坐标的格式略有不同(例如 dec_deg)时，它会出现一些问题。在这种情况下，无法正确识别字符串的第一个或第二个数字。我刚刚编译了一个包含这样坐标的列表:

坐标 = c("-53°30''30.54'", “s55°30' 30.54”， “55°30'30.54n”， “0°1 0.5S”， “-0°30'30''s”， “S55 30 30”， “-55°30'30''”， “-55°30'30''”， “-55°30'30”， “-55 有时文本休息 30 30''”， “55°30'30,54S”， “S55° 30' 30,54”， “-55°30'30.54''”， “-55.5432 30 30.54”， “-55.30.30”， “55.555”， “55,555S”， “S55,555”, “S55.555”， “55,555°S”， “55.555°”， “-55,555”, “-55.555”

       )

Answer 1

它似乎与stringr一起工作正常...

library(stringr)
str_extract_all(str_replace_all(coords, ",", "."), "[0-9.\\-]+")

[[1]]
[1] "-53"   "30"    "30.54"

[[2]]
[1] "55"    "30"    "30.54"

[[3]]
[1] "55"    "30"    "30.54"

[[4]]
[1] "0"   "1"   "0.5"

[[5]]
[1] "-0" "30" "30"

[[6]]
[1] "55" "30" "30"

[[7]]
[1] "-55" "30"  "30" 

[[8]]
[1] "-55" "30"  "30" 

[[9]]
[1] "-55" "30"  "30" 

[[10]]
[1] "-55" "30"  "30" 

[[11]]
[1] "55"    "30"    "30.54"

[[12]]
[1] "55"    "30"    "30.54"

[[13]]
[1] "-55"   "30"    "30.54"