Pie chart ggplot style is surprisingly hard to make, mainly because ggplot2 did not give us a circle shape to deal with. But I explain how to get around it in my blog pot.
Time series plots in R are totally customizable using the ggplot2 package, and can come out with a look that is clean and sharp. However, you usually end up fighting with formatting the x-axis and other options, and I explain in my blog post.
Making box plots in R affords you many different approaches and features. My blog post will show you easy ways to use both base R and ggplot2 to make box plots as you are proceeding with your data science projects.