When I tried to use knit error message:
[WARNING] This document format requires a nonempty element.
Defaulting to 'nelu.knit' as the title.
To specify a title, use 'title' in metadata or --metadata title="...".
Output created: nelu.html
Try to create a simple Rmd file that you can knit to Word.
The easiest way to do that is with File in the RStudio menu:
File | New File | R Markdown... and then select the Word button and click OK .
An .Rmd-file is then generated for you (but not yet saved).
So save it with an .Rmd extension and click the knitr button.
On my computer it produces a .docx files that is immediately opened by Word.
I think it depends on the settings of your computer if Word opens the file automatically or not.
Anyway: the first lines of the .Rmd file shows the 'YAML' lines that are necessary to let knitr do its work:
---
title: "Untitled"
author: "My name"
date: "2022-08-31"
output: word_document
---
Your warnings suggest that there is something wrong with the YAML lines that you have used.
Yes this warning means that somehow your document is missing a title: or have a title: that cause an issue. Can you share more about the content ?
I am starting new Rmarkdown file like these:
title: "Untitled"
author: "Nelu"
date: "September 10, 2022"
output: word_document
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:
summary(cars)
Including Plots
You can also embed plots, for example:
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.
Your header looks good, but it is essential that this header is started and ended with ---.
Sorry doesn work 
"C:/Users/silhda/ANACON~1/envs/rstudio/Scripts/pandoc" +RTS -K512m -RTS asa.knit.md --to html4 --from markdown+autolink_bare_uris+tex_math_single_backslash --output asa.html --lua-filter "C:\Users\silhda\Documents\R\win-library\4.0\rmarkdown\rmarkdown\lua\pagebreak.lua" --lua-filter "C:\Users\silhda\Documents\R\win-library\4.0\rmarkdown\rmarkdown\lua\latex-div.lua" --self-contained --variable bs3=TRUE --section-divs --template "C:\Users\silhda\Documents\R\win-library\4.0\rmarkdown\rmd\h\default.html" --no-highlight --variable highlightjs=1 --variable theme=bootstrap --mathjax --variable "mathjax-url=https://mathjax.rstudio.com/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML" --include-in-header "C:\Users\silhda\AppData\Local\Temp\RtmpE3pt1k\rmarkdown-stree4420f24a9.html"
[WARNING] This document format requires a nonempty element.
Defaulting to 'asa.knit' as the title.
To specify a title, use 'title' in metadata or --metadata title="...".
Output created: asa.html but asa .html are empty instead of size 713Kb
Can you format your code correctly so that we can check that the Rmd file is ok ?
FAQ: How to Format R Markdown Source
Also can you share the results of rmarkdown::pandoc_version() ?
Thank you !
It is normal code when start new rmatkdown file
It is still good practice to format your code correctly.
Can you share the result of rmarkdown::yaml_front_matter run on your input file ?
Also what are your tools versions ?
I can't reproduce using default template document with latest version of tools.
title: "EXEMPLU"
author: "Dan"
date: "September 12, 2022"
output:
html_document:
toc: yes
pdf_document: default
word_document: default
knitr::opts_chunk$set(echo = TRUE)
summary(cars$dist)
summary(cars$speed)
Below error
"C:/Users/silhda/ANACON~1/envs/rstudio/Scripts/pandoc" +RTS -K512m -RTS etc.knit.md --to html4 --from markdown+autolink_bare_uris+tex_math_single_backslash --output etc.html --lua-filter "C:\Users\silhda\Documents\R\win-library\4.0\rmarkdown\rmarkdown\lua\pagebreak.lua" --lua-filter "C:\Users\silhda\Documents\R\win-library\4.0\rmarkdown\rmarkdown\lua\latex-div.lua" --self-contained --variable bs3=TRUE --section-divs --template "C:\Users\silhda\Documents\R\win-library\4.0\rmarkdown\rmd\h\default.html" --no-highlight --variable highlightjs=1 --variable theme=bootstrap --mathjax --variable "mathjax-url=https://mathjax.rstudio.com/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML" --include-in-header "C:\Users\silhda\AppData\Local\Temp\RtmpQFbmPA\rmarkdown-str6e0383229e2.html"
[WARNING] This document format requires a nonempty element.
Defaulting to 'etc.knit' as the title.
To specify a title, use 'title' in metadata or --metadata title="...".
Output created: etc.html.ETC.html are empty
I instaled Rstudio from Anaconda
You keep posting the same error message, but that don't help us to help you.
I don't use RStudio from anaconda. Useful information:
- Which version of RStudio it is ? Is it the latest ?
- Which version of Pandoc is used ?
rmarkdown::pandoc_version() - Which version of rmarkdown is used ? Did you update to latest ?
With issue like that we can't reproduce, it is sometimes related to the user environment. Please to update the tools. I don't know how Anaconda maintain the software, but if you can use R and R Studio outside of anaconda, especially if they don't have latest version that may fix things