Line breaks in R Markdown text (not code blocks)

Question

Using the tufte_template rmarkdown file, I am trying to make a new paragraph (like \newthought{}, but no caps.) I use two spaces, denoted here by *:

# Introduction

The Tufte-\LaTeX\ [^tufte_latex] document**
**
classes define a style similar to the style Edward Tufte uses in his books...

but get this result:

I have tried \n in place of the second pair of spaces (**) as well, but pandoc throws an error.

pandoc.exe: Error producing PDF from TeX source
Error: pandoc document conversion failed with error 43

Finally, I tried using a <br> tag, but that seems to have no effect whatsoever - it doesn't print the text or a break to the PDF.

I would like a new paragraph, without the indentation, similar to \newthought{}, but without the capitalization...is there a way?

Update 1 with sessionInfo():

> sessionInfo()
R version 3.1.2 (2014-10-31)
Platform: x86_64-w64-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
[1] digest_0.6.8    htmltools_0.2.6 rmarkdown_0.5.1 tools_3.1.2     yaml_2.1.13

Update 2

This seems to be a problem I encounter specifically when using the Tufte template:

Answer 1

I tried these tests, it seems to be working:

test.Rmd

---
output: pdf_document
---

# test 1
No spaces used   

line1
line2


# test 2
2spaces at the end of line1  

line1  
line2

# test 3
2spaces at the end of line1, then 2 spaces on next line

line1  

line2

sessionInfo()
R version 3.2.0 (2015-04-16)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

locale:
[1] LC_COLLATE=English_United Kingdom.1252  LC_CTYPE=English_United Kingdom.1252   
[3] LC_MONETARY=English_United Kingdom.1252 LC_NUMERIC=C                           
[5] LC_TIME=English_United Kingdom.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
[1] htmltools_0.2.6 tools_3.2.0     yaml_2.1.13     rmarkdown_0.5.1 digest_0.6.8 

Answer 2

It's a rather old question, but I post an answer since it's the first hit when googling for "line breaks in rmarkdown".

If compiling to pdf, you can use latex macros. Substitute the ** in the new line with \hfill\break:

# Introduction

The Tufte-\LaTeX\ [^tufte_latex] document**
\hfill\break
classes define a style similar to the style Edward Tufte uses in his books...