nest() data frames then iterate with purrr::map()

code available at https://github.com/libjohn/workshop_rfun_iterate full video series -- playlist -- https://www.youtube.com/watch?v=PrUnbYlC1kY&list=PLIUcX1JrVUNWW7RgPh9ysmJM3mBpIAlYG Using the case-study of data cleaning, this modular video series will demonstrate **iteration** with **`purrr::map()`** and **custom functions** while also showing several Tidyverse tips and tricks. This individual video (# 4) in the series presents the technique of nesting data frames as a step towards iteration using the purrr library and the map() functions. Each #IterateFunctionsR video will become progressively more fluent, using building-blocks to present intermediate data manipulation techniques in R and the Tidyverse. By the end of the series you'll learn how to use the purrr package, a very convenient package in support of iterating over list-columns and nested data frames. purrr::map() iteration is often more convenient and efficient than a **For-loop**. You'll also learn how to compose custom functions in R. since R is a functional programming language, composing your own custom functions can increase your fluency as an R coder. Materials available at https://github.com/libjohn/workshop_rfun_iterate More Rfun at https://Rfun.library.duke.edu/ Part of the CDVS Workshop Series: http://library.duke.edu/data/