I would like to get longitude/latitude data for the cities in my dataframe and add as 2 columns in my frame. I'm new to R and I do not know how to do it. Could someone help me on this
My frame:
> data <- read.xlsx("example_city.xlsx", 1)
> data
City Country
1 Stockholm Sweden
2 Oslo Norway
3 Rome Italy
4 Rome Italy
5 Stockholm Sweden
6 Stockholm Sweden
7 Paris France
8 Paris France
9 Hamburg Germany
10 Paris France
11 Paris France
lukeA
With reference to your original question https://stackoverflow.com/questions/20936263/use-ggplot2-to-plot-cities-on-a-map
# data
cities <- sort(c(rep('Stockholm', 3), 'Oslo', 'Rome', 'Rome', 'Paris', rep('Bonn',10), 'Paris', 'Paris', 'Stockholm'))
# 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)
# get matches between names {maps} names and EU country names
library(maps)
eu <- c("Austria", "Belgium", "Bulgaria", "Croatia", "Cyprus", "Czech Republic",
"Denmark", "Estonia", "Finland", "France", "Germany", "Greece",
"Hungary", "Ireland", "Italy", "Latvia", "Lithuania", "Luxembourg",
"Malta", "Netherlands", "Poland", "Portugal", "Romania", "Slovakia",
"Slovenia", "Spain", "Sweden", "United Kingdom")
warning("No matches in database for ", paste(setdiff(eu, map_data('world')$region), collapse=", "))
europe <- map_data('world', region=eu)
# plot
library(ggplot2)
ggplot(europe, aes(x=long, y=lat, group=group)) +
geom_polygon(fill="white", colour="black") +
xlim(-20, 40) + ylim(25,75) +
geom_point(data=cities, inherit.aes=F, aes(x=lon, y=lat, size=Freq), colour="red", alpha=.8) +
geom_text(data=cities, inherit.aes=F, aes(x=lon, y=lat, label=cities), vjust=1, colour="red", alpha=.5)
来源：https://stackoverflow.com/questions/20936840/r-get-longitude-latitude-data-for-cities-and-add-it-to-my-dataframe