How to add geo-spatial connections on a ggplot map?

Question

Using this as a reference, I\'m trying to plot a map of the lower forty-eight and add layers to visualize flow between states.

library(ggplot2)
library(maps)         


        

Answer 1

gcIntermediate returns different column names (since origin and destination is identical for i=2):

for (i in 1:3) {
  inter <- as.data.frame(gcIntermediate(c(geo[i,]$orig_lon, geo[i,]$orig_lat), 
                                        c(geo[i,]$dest_lon, geo[i,]$dest_lat), 
                                        n=50, addStartEnd=TRUE))
  print(head(inter, n=2))
}
     lon   lat
1 -119.7 36.17
2 -119.6 36.13
      V1    V2
1 -119.7 36.17
2 -119.7 36.17
     lon   lat
1 -119.7 36.17
2 -119.5 36.24

The following lines should work:

for (i in 1:3) {
  inter <- as.data.frame(gcIntermediate(c(geo[i,]$orig_lon, geo[i,]$orig_lat), 
                                        c(geo[i,]$dest_lon, geo[i,]$dest_lat), 
                                        n=50, addStartEnd=TRUE))
  names(inter) <- c("lon", "lat")
  p <- p + geom_line(data=inter, aes(x=lon, y=lat), color='#FFFFFF')
}