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

Question

I recently posted a question regarding plotting postions on cities in europe as points on a map. See R, get longitude/latitude data for cities and add it to my dataframe

cities xlsx file contains about 20000 cities in europe.

I got an error message when trying to find the latitude/longitude data using geocode. I have inserted part of the code below:

cities <- read.xlsx("EU_city.xlsx",1)

# get frequencies
freq <- as.data.frame(table(cities))
library(plotrix)
freq$Freq <- rescale(freq$Freq, c(1,10)) # c(scale_min, scale_max)

# get cities latitude/longitude - kindly provided by google:
library(ggmap)
lonlat <- geocode(unique(cities)) 
cities <- cbind(freq, lonlat)

error message:

Error: is.character(location) is not TRUE

I guess the data(cities) in my dataframe is not found in the geocode call. Is there a way to ignore the city in the dtaframe if it is not matched in geocode

Update of question after suggestion.......

tried geocode(as.character(cities))

Then my frame looks like this:

> cities <- cbind(freq, lonlat)
> cities
                       cities  Freq lon lat
1                      ARNHEM  1.00  NA  NA
2                      ATHENS  3.25  NA  NA
3                        BAAR  1.00  NA  NA
4                BAD  VILBEL   1.00  NA  NA
5                   BILTHOVEN  1.00  NA  NA
6                      BOCHUM 10.00  NA  NA
7                       BREDA  3.25  NA  NA
8              CAMBRIDGESHIRE  3.25  NA  NA
9                   DORDRECHT  1.00  NA  NA
10                GAOETERSLOH  1.00  NA  NA
11              GELSENKIRCHEN  1.00  NA  NA
12                       GOES  1.00  NA  NA
13                  GRONINGEN  3.25  NA  NA
14  GUMMERSBACH-DIERINGHAUSEN  1.00  NA  NA
15                  HALSTEREN  1.00  NA  NA
16                   HANNOVER  1.00  NA  NA
17                 HARDERWIJK  1.00  NA  NA
18                    HEERLEN  3.25  NA  NA
19                  HILVERSUM  1.00  NA  NA

I got no long/lat data at all, only NA

Answer 1

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)