R trying to find latitude/longitude data for cities in europe and getting geocode error messege

You have to geocode just the cities column (it's a little confusing that you have a data frame called cities, and within it a column called cities). When in doubt, try breaking things down into smaller chunks.

For example, try them one at a time ...

cities <- c("ARNHEM","ATHENS","BAAR","CAMBRIDGESHIRE")
library(ggmap)
geocode(cities[1])
##       lon     lat
## 1 5.89873 51.9851
geocode(cities[2])
## just checking ...
geocode("ATHENS GEORGIA")
##         lon   lat
## 1 -83.38333 33.95

Now try the vector all at once:

geocode(cities)
##          lon      lat
## 1  5.8987296 51.98510
## 2 23.7293097 37.98372
## 3  8.5286332 47.19585
## 4  0.0965375 52.27619

Now try with a data frame:

mydat <- read.csv(textConnection("
   cities,Freq,lon,lat
   ARNHEM,1.00,NA,NA
   ATHENS,3.25,NA,NA
   BAAR,1.00,NA,NA
   BAD VILBEL,1.00,NA,NA
   BILTHOVEN,1.00,NA,NA
   BOGUS_PLACE,2,NA,NA"))


geocodes <- geocode(as.character(mydat$cities))
mydat <- data.frame(mydat[,1:2],geocodes)

##               cities Freq        lon      lat
## 1             ARNHEM 1.00   5.898730 51.98510
## 2             ATHENS 3.25  23.729310 37.98372
## 3               BAAR 1.00   8.528633 47.19585
## 4         BAD VILBEL 1.00   8.739480 50.18234
## 5          BILTHOVEN 1.00   5.210381 52.13653
## 6        BOGUS_PLACE 2.00 -92.201158 44.49091

I don't know what the result for BOGUS_PLACE means ...!!

I have just found that this error message:

Error: is.character(location) is not TRUE

can be due to the address being encoded as a number, not a character. This can happen when you select from a data frame for instance, which was my case.

Do:

typeof(address)

and if it turns out to be numeric, change it to char

a2 <- as.character(address)
geocode(a2)