I have a quite simple question I suppose. If I draw a scatter plot like this:
data <- data.frame(lon=runif(100)*3+10, lat=runif(100)*5+42, value=rnorm(100)*100)
ggplot() + geom_point(aes(x=lon, y=lat, color=value), data=data)
the legend is properly displayed and the breaks are specified.
but when i use a map as background:
SHmap <- qmap(c(lon=mean(data[,'lon'], na.rm=TRUE), lat=mean(data$lat, na.rm=TRUE)), zoom=7)
SHmap <- SHmap + geom_point(aes(x=lon, y=lat, color=value), data=data)
SHmap
am I doing something wrong or is this behaviour intended?