R Markdown YAML "Scanner error: mapping values..." - yaml

Question

I have noticed this issue when knitting all file types (html, pdf, word). To make sure there's not an issue specific to my program, I went ahead and ran the default .rmd file you get when you create a new markdown. In each case, it does knit correctly, but I always see this at the end. I have searched online and here but cannot seem to find an explanation
Error in yaml::yaml.load(string, ...) :
Scanner error: mapping values are not allowed in this context at line 6, column 19
Error in yaml::yaml.load(string, ...) :
Scanner error: mapping values are not allowed in this context at line 6, column 19
Error in yaml::yaml.load(string, ...) :
Scanner error: mapping values are not allowed in this context at line 4, column 22
Here is my default YAML
---
title: "Untitled"
author: "Scott Jackson"
date: "April 20, 2017"
output: word_document
---
Line 4, column 22 is the space between the 7 and "
I'm not sure where Line 6, column 19 is, but that line is the dashes at the bottom
Any ideas?
Thank you.

Answer 1

I get this error when trying to add a table of contents to the YAML:
title: "STAC2020 Data Analysis"
date: "July 16, 2020"
output: html_notebook:
toc: true
However, if I put html_notebook: on to a separate line then I don't get the error:
title: "STAC2020 Data Analysis"
date: "July 16, 2020"
output:
html_notebook:
toc: true
I do not know why this formatting makes a difference, but it allowed my document to knit and with a table of contents.

Answer 2

I realize this question has gone unanswered for awhile, but maybe someone can still benefit. I had the same error message and I realized I had an extra header command in my yaml. I can't reproduce your exact error, but I get the same message with different line/column references with:
---
title: "Untitled"
author: "Scott Jackson"
date: "April 20, 2017"
output: output: word_document
---
Error in yaml::yaml.load(string, ...) :
Scanner error: mapping values are not allowed in this context at line 4, column 15
Calls: <Anonymous> ... parse_yaml_front_matter -> yaml_load_utf8 -> <Anonymous>
Execution halted
Line 4 column 15 seems to refer to the second colon after the second "output".

Answer 3

I received this error when there was an indentation in the wrong place:
For example, the indentation before header-includes as seen in the example code below caused the error
---
title: "This is a title"
author: "Author Name"
header-includes:
.
.
.
---
When you remove the indentation, the following code below did not produce the error:
---
title: "This is a title"
author: "Author Name"
header-includes:
.
.
.
---

Answer 4

Similarly to Tim Ewers I also got this error when I added a TOC to the YAML:
title: "My title"
date: "April 1, 2020"
output:
pdf_document: default
toc: true
html_document: paged
However, the solution I found was to remove "default", this allowed me to knit the document without an error:
title: "My title"
date: "April 1, 2020"
output:
pdf_document:
toc: true
html_document: paged

Answer 5

I guess this error happens on your content instead of your yaml block.
Because there is no extra content display so I will give a minimal example.
> library(yaml)
> library(magrittr)
> "
+ ---
+ title: 'This is a title'
+ output: github_document
+ ---
+
+ some content
+ " %>%
+ yaml.load()
$title
[1] "This is a title"
$output
[1] "github_document"
It works well. And here is another example.
> "
+ ---
+ title: 'This is a title'
+ output: github_document
+ ---
+
+ some content
+ some content: some content
+ " %>%
+ yaml.load()
Error in yaml.load(.) :
Scanner error: mapping values are not allowed in this context at line 8, column 13
The errors happens at line 8. Because there is a key-value pair not at yaml block.
yaml.load is not enough smart for me.
The temporal solution for me is just extract all lines above the second ---.
> text <- "
+ ---
+ title: 'This is a title'
+ output: github_document
+ ---
+
+ some content
+ some content: some content
+ "
> library(xfun)
> read_lines(text,n_max = 5) %>%
+ yaml.load()
$title
[1] "This is a title"
$output
[1] "github_document"

Answer 6

I had a similar problem and made a request in the YAML and rticles help pages:
https://github.com/viking/r-yaml/issues/92
https://github.com/rstudio/rticles/issues/363

Answer 7

I know this is a 5 year old question but I just got this same error as I was missing a colon
---
title: ''
output:
pdf_document
includes:
before_body: before_body.tex
---
should have been
---
title: ''
output:
pdf_document:
includes:
before_body: before_body.tex
---
and while that doesn't strictly answer the example given, I hope it will help future sufferers of this error message.