Escaped-RMarkdown-Params.RmD

---
title: "Escaping R Code in RMarkdown Paramaters"
author: "Alex Axthelm"
date: "6/23/2017"
output: html_document
params:
  unescaped_add: 1 + 1
  unescaped_fun: rnorm(10)
  escaped_add: !r 1 + 1
  escaped_fun: !r rnorm(10)
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
# Basic Magic Demo

Let's explore the magic of escaping paramaters in R markdown.

First, Let's look at what an unescaped paramater looks like:
```{r}
params$unescaped_add
params$unescaped_fun
```

Notice that these are evaluated as literal strings. R doesn't do any evaluation of the code inside

## BUT!

Let's see what happens when we escape our R code using `!r`:

```{r}
params$escaped_add
params$escaped_fun
```

Remember that these `params` need to be defined in YAML header, or when calling `rmarkdown::render`

## Note: It's not actually a function call

Let's revisit `escaped_fun`. A person might be inclined to believe that R is evaluating that when it reads the YAML. That person is exactly correct:

```{r}
# It's the same as above
params$escaped_fun

#still the same values, because the values are stored not evaluated:
set.seed(42)
params$escaped_fun
```