eliminating words until the result is defined - r

Question

I'm currently making code returning the lat and long of the address by using geocode.
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]))
if the address in the name sentence have no result in google, it automatically returns NA for lat an long.
Therefore how can I keep eliminating the words until there is a result (Usually, if the address is too specified, there is no result). In this case, if "720-37, chorok-ro" is eliminated, it works.

Answer 1

As I mentioned in my comment, I can use the geocode function from the ggmap package to geocode the address you provided, so it is not a good test case. I thus changed your test case by adding two new words in the beginning.
# Test case
name <- "Alpha, Beta, 720-37, Chorok-ro, Yanggam-myeon, Hwaseong-si, Gyeonggi-do, Republic of Korea"
Here I showed that the standard geocode function will not work.
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"
And then I designed a function to conduct "stepwise" geocode, which uses a while-loop to check if there are results. If not, remove the first word and then try again until there are results.
# 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)
}
We can test the function as follows.
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"
Finaly, if there are no any words will work, the function will still return a data frame with 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"