@article{JSSv015i05,
title={Proportional Symbol Mapping in R},
volume={15},
url={https://www.jstatsoft.org/index.php/jss/article/view/v015i05},
doi={10.18637/jss.v015.i05},
abstract={Visualization of spatial data on a map aids not only in data exploration but also in communication to impart spatial conception or ideas to others. Although recent carto-graphic functions in R are rapidly becoming richer, proportional symbol mapping, which is one of the common mapping approaches, has not been packaged thus far. Based on the theories of proportional symbol mapping developed in cartography, the authors developed some functions for proportional symbol mapping using R, including mathematical and perceptual scaling. An example of these functions demonstrated the new expressive power and options available in R, particularly for the visualization of conceptual point data.},
number={5},
journal={Journal of Statistical Software},
author={Tanimura, Susumu and Kuroiwa, Chusi and Mizota, Tsutomu},
year={2006},
pages={1–7}
}