GitHub 主页：
https://github.com/wilkelab/cowplot
CRAN 包地址：
http://cran.r-project.org/web/packages/cowplot/index.html
包描述：
The cowplot package is a simple add-on to ggplot2. It is meant to provide a publication-ready theme for ggplot2, one that requires a minimum amount of fiddling with sizes of axis labels, plot backgrounds, etc. Its primary purpose is to give my students and postdocs an easy way […]