r - gmmap with zoom=1 not displaying

Question

I am trying to plot a world map using zoom=1 in the code below and it is not displaying, but when I put any other zoom number (for example 4) it is working perfectly...

Any idea why it is not working with zoom=1?

library(ggmap)
map <- qmap('world', zoom = 1)
map

Answer 1

according to the documentation here http://cran.r-project.org/web/packages/ggmap/ggmap.pdf

"Map zoom, an integer from 3 (continent) to 21 (building), default value 10 (city).Openstreetmaps limits a zoom of 18, and the limit on stamen maps depends on the maptype. ’auto’ automatically determines the zoom for bounding box specifications, and is defaulted to 10 with center/zoom specifications. Maps of the whole world currently not supported."