For use internally.
choropleth.spplot(sp, dem = "P0010001", cuts = list("quantile", seq(0, 1, 0.25)),
color = list(fun = "hsv",
attr = list(h = c(0.4, 0.5, 0.6, 0.7), s = 0.6, v = 0.6, alpha = 1)),
main = NULL, sub = "Quantiles (equal frequency)",
legend = list(pos = "bottomleft",
title = "Population Count"), border = "transparent", object = NULL, ...)
Zack W. Almquist (2010). US Census Spatial and Demographic Data in R: The UScensus2000 Suite of Packages. Journal of Statistical Software, 37(6), 1-31. https://www.jstatsoft.org/v37/i06/.