如何从ggmap获取黑白地图？

Question

If I use a state name as the first argument like so:

map <- ggmap::get_map("Louisiana", zoom=3, maptype = "toner-background", source="stamen")

then I get the black and white map that I want like so:

But If I enter the first argument with longitude and latitude coordinates like so:

map <- ggmap::get_map(c(left=-120, bottom=-65, right=5, top=70), zoom = 3, maptype = "toner-background", source="stamen")

Then i always get a map like this:

The other parameters seem to have no effect.

My goal is to call this function with coordinates like the second line of code and get a black and white map like in the first case.

Answer 1

This issue of getting a Google Terrain map when you wanted a Stamen map is one that I saw recently in another context. Instead of using the generic get_map function, try the specific get_stamenmap like this:

library(ggmap)

ggmap(get_stamenmap(c(left=-120, bottom=-65, right=5, top=70), zoom = 3, 
                    maptype = "toner-background"))

Answer 2

If you've already downloaded the colored images, you have to use force = TRUE argument

Eg,

map = get_stamenmap(your-map, maptype = "toner-background", color="bw", force=T)