R: Error in get_map()/get_googlemap() from ggmap

问题

I am trying to use GGmap to create a plot of vehicle car crashes by state. The map will have dots which are sized based on the number of car crashes in the state.

In particular I am trying to recreate the usa-plot shown in the visualizing clusters section of this blog post.

However, whenever I try to create the map I get this error.

Error in aperm.default(map, c(2, 1, 3)) : 
  invalid first argument, must be an array

I have setup the Google API and see that it is recieving hits. I have also enabled it and have the key.

In addition I have installed GGmap from the github account using this command:

devtools::install_github("dkahle/ggmap", ref = "tidyup", force=TRUE)

since the CRAN one isn't updated.

I have restarted and quit R several times as well but the error persists.

Even if I just simply run:

get_map()

it still results in the error:

Error in aperm.default(map, c(2, 1, 3)) : 
      invalid first argument, must be an array

Below is my code, it is similar to the code in the blog post:

mydata$State <- as.character(mydata$State)
mydata$MV.Number = as.numeric(mydata$MV.Number)
mydata = mydata[mydata$State != "Alaska", ]
mydata = mydata[mydata$State != "Hawaii", ]
devtools::install_github("dkahle/ggmap", ref = "tidyup", force=TRUE)
library(ggmap)
ggmap::register_google(key = "...") #my key is here
for (i in 1:nrow(mydata)) {
  latlon = geocode(mydata[i,1])
  mydata$lon[i] = as.numeric(latlon[1])
  mydata$lat[i] = as.numeric(latlon[2])
}
mv_num_collisions = data.frame(mydata$MV.Number, mydata$lon, mydata$lat)

colnames(mv_num_collisions) = c('collisions','lon','lat')
usa_center = as.numeric(geocode("United States"))


USAMap = ggmap(get_googlemap(center=usa_center, scale=2, zoom=4), 
extent="normal")
USAMap + 
   geom_point(aes(x=lon, y=lat), data=mv_num_collisions, col="orange", 
alpha=0.4, size=mv_num_collisions$collisions*circle_scale_amt) +  
   scale_size_continuous(range=range(mv_num_collisions$collisions))

I expect the map to output like this

But I cannot seem to get passed this error.

If anyone can help that would be great.

Please let me know if you need any more information.

Thank you.