Converting Rmarkdown to PDF without RStudio - r

Question

I would like to convert a *.Rmd to document to PDF without rstudio being available.
Current approach
Current approach follows the following steps:
*.Rmd document is passed to knitr: knit(input = "report.Rmd"))
Obtained md is converted via pandoc:
# Convert
pandoc --smart --to latex \
--latex-engine pdflatex \
-s report.md \
-o report.PDF
Problems
This results in the following problems, the top section of the Rmarkdown document:
---
title: "Report Title"
author: "Person"
output: pdf_document
classoption: landscape
---
and shows as:
all text is centered, whereas I would like for it to be left-aligned:
Possible approach
I would like to make use of the rmarkdown::render; however, despite setting RSTUDIO_PANDOC (as discussed here), the command fails on pandoc not being available.
Desired outcome
I don't care much whether the utilised mechanism makes use of the rmarkdown::render, what I want to achieve is:
Landscape page layout across all pages
Left-aligned text
Ability to exercise minimum control over the document by controlling default fonts
Ideally, I would like to do as much as in the *.Rmd file as possible without the need to add parameters to the pandoc command.
Updates, following comments
I'm working on Linux and pandoc is installed, I can execute pandoc command pass files and generate exports with no problems. It only doesn't work with the rmarkdown::render package.
Concerning the hooks and *.Rmd files, this is what I'm trying to understand as I see that that the first section of my *.Rmd file is ignored. The current process looks as follows:
*.Rmd (not much in it, just title section and dummy text and code that renders but wrongly justified) >
*.R file running one line knit(input = "report.Rmd")) >
*.sh file running pandoc command and generating PDF
Concerning:
if all that is in place, it is indeed just a call to
rmarkdown::render(...)
The rmarkdown::render(...) fails:
Error: pandoc version 1.12.3 is required and was not found ...
However:
>> rmarkdown::pandoc_available()
[1] TRUE
and:
$ pandoc -v
pandoc 1.9.4.1 (...)
The RSTUDIO_PANDOC points to pandoc.

Answer 1

A few things:
"the command fails on pandoc not being available." well you must have pandoc installed in order to call it -- but you didn't say what OS you have. On Linux it is pretty trivial to install pandoc from the package manager; otherwise jgm has binaries for you on the site; "should" be similar on OS X
for different styling you need to modify the LaTeX code which you can via numerous hooks to include macro files; see the RMarkdown cheat sheets for detail
if you want to exercise more control, you can supply your own template; I have done so in the tint package
(which is also on CRAN)
if all that is in place, it is indeed just a call to rmarkdown::render(...)

Answer 2

Error: pandoc version 1.12.3 is required and was not found
I think the error says it plainly: you need pandoc 1.12.3 and you have pandoc 1.9.4.1
I do not know, however, why such a specific version is required.