linebreak + %

demo.Rmd

---
title: "Untitled"
author: "Hao"
date: "7/10/2019"
output: pdf_document
---

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

## R Markdown

This is an R Markdown document. Markdown is a simple formatting syntax for authoring HTML, PDF, and MS Word documents. For more details on using R Markdown see <http://rmarkdown.rstudio.com>.

When you click the **Knit** button a document will be generated that includes both content as well as the output of any embedded R code chunks within the document. You can embed an R code chunk like this:

```{r cars}
library(kableExtra)
header <- setNames(c(1, 3), c(" ", linebreak(
  "OR\n(95\\\\%CI)", align = "c", double_escape = T
)))

linebreak("a\nb")

kable(mtcars[1:3], "latex", booktabs = T) %>%
  add_header_above(header, escape = F)
```

## Including Plots

You can also embed plots, for example:

```{r pressure, echo=FALSE}
plot(pressure)
```

Note that the `echo = FALSE` parameter was added to the code chunk to prevent printing of the R code that generated the plot.