Change line spacing for RMD abstract?

问题

Is it possible to change the line spacing for the abstract specified in my YAML header to single space, while leaving the rest of the document in double space? My YAML is below:

output:  pdf_document
number_sections: true
title: | 
  | My Title
author: 
- Me
header-includes:
    - \usepackage{setspace}\doublespacing
    - \usepackage{float}
abstract: "My abstract"
keywords: "My keywords"
date: "`r format(Sys.time(), '%B %d, %Y')`"
geometry: margin=1in
fontsize: 12pt
spacing: double
fig_caption: yes
indent: true
---

I've tried wrapping the abstract like so, but it did not work:

abstract: 
    - \usepackage{setspace}\singlespacing
"My abstract"
    - \end{singlespacing}

回答1:

The abstract is automatically wrapped, so it is enough to use \singlespacing before it:

---
output:  pdf_document
number_sections: true
title: | 
  | My Title
author: 
- Me
header-includes:
    - \usepackage{setspace}\doublespacing
    - \usepackage{float}
abstract: \singlespacing My abstract which has to be long enough to take multiple
  lines otherwise one does not see the effect of single-spacing.
keywords: "My keywords"
date: "`r format(Sys.time(), '%B %d, %Y')`"
geometry: margin=1in
fontsize: 12pt
fig_caption: yes
indent: 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>.

Result:

来源：https://stackoverflow.com/questions/52118202/change-line-spacing-for-rmd-abstract