About the Authors

Yanguang Chen

chenyg@pku.edu.cn

Affiliation Department of Geography, College of Urban and Environmental Sciences, Peking University, 100871, Beijing, China

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Performed the experiments: YC. Analyzed the data: YC. Contributed reagents/materials/analysis tools: YC. Wrote the paper: YC. Wrote an instruction using MS Word: YC. Made a calculation example using MS Excel: YC. Wrote programs based on Matlab: YC.