Code chunks

4. Set up a network of chunks where d depends on c and b, and both b and c depend on a. Have each chunk print lubridate::now(), set cache = TRUE, then verify your understanding of caching.

---
title: "Exercise 24.4.7.4"
author: "Joey Campbell"
date: "03/19/2019"
output: html_document
---

`{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE, cache = TRUE)
`

The chunk `a` has no dependencies.
`{r a}
print(lubridate::now())
x <- 1
`

The chunk `b` depends on `a`.
`{r b, dependson = c("a")}
print(lubridate::now())
y <- x + 1
`

The chunk `c` depends on `a`.
`{r c, dependson = c("a")}
print(lubridate::now())
z <- x * 2
`

The chunk `d` depends on `c` and `b`:
`{r d, dependson = c("c", "b")}
print(lubridate::now())
w <- y + z
`

If this document is knit repeatedly, the value printed by lubridate::now() will be the same for all chunks, and the same as the first time the document was run with caching.