消除单词直到定义结果

Question

我目前正在使用地理编码编写返回地址经纬度的代码。

library(ggmap)

name <- "720-37, Chorok-ro, Yanggam-myeon, Hwaseong-si, Gyeonggi-do, Republic of Korea"
address <- geocode(name)
df <- data.frame(lat = as.numeric(address[2]), lon = as.numeric(address[1]))

如果name语句中的地址在google中没有结果，它会自动returns NA for lat an long。

所以我怎么一直删字直到有结果（一般地址指定的太细了，是没有结果的）。在这种情况下，如果“720-37，chorok-ro”被消除，它就起作用了。

Answer 1

正如我在评论中提到的，我可以使用 ggmap 包中的 geocode 函数对您提供的地址进行地理编码，因此这不是一个好的测试用例。因此，我通过在开头添加两个新词来更改您的测试用例。

# Test case
name <- "Alpha, Beta, 720-37, Chorok-ro, Yanggam-myeon, Hwaseong-si, Gyeonggi-do, Republic of Korea"

这里我展示了标准的geocode函数是行不通的

library(ggmap)
geocode(name)
Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=Alpha,%20Beta,%20720-37,%20Chorok-ro,%20Yanggam-myeon,%20Hwaseong-si,%20Gyeonggi-do,%20Republic%20of%20Korea&sensor=false
  lon lat
1  NA  NA
Warning message:
geocode failed with status ZERO_RESULTS, location = "Alpha, Beta, 720-37, Chorok-ro, Yanggam-myeon, Hwaseong-si, Gyeonggi-do, Republic of Korea"

然后我设计了一个函数来进行"stepwise"地理编码，它使用while-loop来检查是否有结果。如果没有，请删除第一个单词，然后重试直到有结果。

# A function to perform the geocode by step-wise eliminating the word from the top
geocode_step <- function(name){
  # Perform geocode
  coords <- geocode(name)
  # Use while loop to check the result, if both lat and lon are NA
  # Remove the first word and then try again
  while (is.na(coords[[1]]) & is.na(coords[[2]])){
    name_vec <- strsplit(name, split = ",")[[1]][-1]
    # All words are eliminated, stop the function and return a data frame with NA and warning
    if (length(name_vec) == 0){
      break
    }
    # Re-combine all words
    name <- paste(name_vec, collapse = ", ")
    # Conduct geocode again
    coords <- geocode(name)
  }
  dat <- data.frame(lon = coords[[1]], lat = coords[[2]], name = name)
  return(dat)
}

我们可以如下测试功能

geocode_step(name)
Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=Alpha,%20Beta,%20720-37,%20Chorok-ro,%20Yanggam-myeon,%20Hwaseong-si,%20Gyeonggi-do,%20Republic%20of%20Korea&sensor=false
Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=%20Beta,%20%20720-37,%20%20Chorok-ro,%20%20Yanggam-myeon,%20%20Hwaseong-si,%20%20Gyeonggi-do,%20%20Republic%20of%20Korea&sensor=false
Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=%20%20720-37,%20%20%20Chorok-ro,%20%20%20Yanggam-myeon,%20%20%20Hwaseong-si,%20%20%20Gyeonggi-do,%20%20%20Republic%20of%20Korea&sensor=false
       lon      lat
1 126.9827 37.11354
                                                                                       name
1   720-37,   Chorok-ro,   Yanggam-myeon,   Hwaseong-si,   Gyeonggi-do,   Republic of Korea
Warning messages:
1: geocode failed with status ZERO_RESULTS, location = "Alpha, Beta, 720-37, Chorok-ro, Yanggam-myeon, Hwaseong-si, Gyeonggi-do, Republic of Korea" 
2: geocode failed with status ZERO_RESULTS, location = " Beta,  720-37,  Chorok-ro,  Yanggam-myeon,  Hwaseong-si,  Gyeonggi-do,  Republic of Korea"

最后，如果没有任何词会起作用，该函数仍将 return 一个数据框 NA。

geocode_step("aawsd")
Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=aawsd&sensor=false
  lon lat  name
1  NA  NA aawsd
Warning message:
geocode failed with status ZERO_RESULTS, location = "aawsd"

消除单词直到定义结果

eliminating words until the result is defined

for-loop

r

geolocation

ggmap