Minimal self-compiling to .pdf Rmarkdown file - linux

Question

I need to compose a simple rmarkdown file, with text, code and the results of executed code included in a resulting PDF file. I would prefer if the source file is executable and self sifficient, voiding the need for a makefile.
This is the best I have been able to achieve, and it is far from good:
#!/usr/bin/env Rscript
library(knitr)
pandoc('hw_ch4.rmd', format='latex')
# TODO: how to NOT print the above commands to the resulting .pdf?
# TODO: how to avoid putting everyting from here on in ""s?
# TODO: how to avoid mentioning the file name above?
# TODO: how to render special symbols, such as tilde, miu, sigma?
# Unicode character (U+3BC) not set up for use with LaTeX.
# See the inputenc package documentation for explanation.
# nano hw_ch4.rmd && ./hw_ch4.rmd && evince hw_ch4.pdf
"
4E1. In the model definition below, which line is the likelihood?
A: y_i is the likelihood, based on the expectation and deviation.
4M1. For the model definition below, simulate observed heights from the prior (not the posterior).
A:
```{r}
points <- 10
rnorm(points, mean=rnorm(points, 0, 10), sd=runif(points, 0, 10))
```
4M3. Translate the map model formula below into a mathematical model definition.
A:
```{r}
flist <- alist(
y tilda dnorm( mu , sigma ),
miu tilda dnorm( 0 , 10 ),
sigma tilda dunif( 0 , 10 )
)
```
"
Result:

Answer 1

What I eventually came to use is the following header. At first it sounded neat, but later I realized
+ is indeed easy to compile in one step
- this is code duplication
- mixing executable script and presentation data in one file is a security risk.
Code:
#!/usr/bin/env Rscript
#<!---
library(rmarkdown)
argv <- commandArgs(trailingOnly=FALSE)
fname <- sub("--file=", "", argv[grep("--file=", argv)])
render(fname, output_format="pdf_document")
quit(status=0)
#-->
---
title:
author:
date: "compiled on: `r Sys.time()`"
---
The quit() line is supposed to guarantee that the rest of the file is treated as data. The <!--- and --> comments are to render the executable code as comments in the data interpretation. They are, in turn, hidden by the #s from the shell.