r ggplot scale_fill_gradient breaks
+ scale_fill_gradient(high = "springgreen4", low= "grey90", name="Sum",
labels = c("5,000,000", "4,000,000", "3,000,000", "2,000,000", "1,000,000"),
breaks = c(5000000, 4000000, 3000000, 2000000, 1000000))