Honestly your best bet may be to try running the query again. The results seem pretty idiosyncratic as far as I can tell (possibly related to dynamic IPs over WiFi?). These are my results from just now.
df %>% mutate_geocode(address)
Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=Sukkur&sensor=false
address lon lat
1 Sukkur NA NA
Warning message:
geocode failed with status OVER_QUERY_LIMIT, location = "Sukkur"
So it failed for me too. I checked the queries I had left, then added "Paris" to check its results.
geocodeQueryCheck()
2499 geocoding queries remaining.
df
address
1 Sukkur
df[2,1]<-"Paris"
df %>% mutate_geocode(address)
Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=Sukkur&sensor=false
Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=Paris&sensor=false
address lon lat
1 Sukkur 68.822808 27.72436
2 Paris 2.352222 48.85661
And now it works!
The issue may be helped by obtaining a Google Maps API key as this question suggests, which you can use if you install the GitHub version of ggmap
.
The other option is to iterate through requests as an answer here suggests.