R Markdown: displaying summation command in PDF output - r

I'm brand new to R, as in my class just began two days ago. In our first assignment we are to show our work and answers, which are written in R Markdown (inside R Studio) and then output in PDF.
On one question we are asked to display the quadratic equation. I know the command, which I figured out is $$ x=\frac{ -b \pm \sqrt{ b^2 - 4ac} }{2a} $$.
After I Knit the file to PDF the equation shows up all nice and pretty. However, I cannot figure out how to also get the command to also display to show my work. If I prefix the command with an asterisk, backslash, hashtag, etc., after I knit the file it shows the prefix and then just displays the quadratic equation but not the command.
I'd ask my prof, but he actually suggested we try Stack Overflow with questions in the syllabus (haha!), then referred to himself as a "facilitator more than a teacher". Hmmm. So here I am.

One option is to insert a chunk with your equation:
```
$$ x=\frac{ -b \pm \sqrt{ b^2 - 4ac} }{2a} $$.
```

Related

Writing mathematical equation in jupyter notebook in a markdown (.md) file

I have written a document in the jupyter notebook as a markdown (.md) file. The document contains some mathematical equation which I have written inside $$ equation $$, for example,
$$c = \sqrt{a^2 + b^2}$$
Now, when I push the .md file in the Gitlab, my equations are appearing in the latex format, like
$$c = \sqrt{a^2 + b^2}$$
The file was okay when I did the print preview but in the GitLab the equations are appearing inside $$...$$.
Could you pls help me to resolve the issue?
Thanks!!
I have found a solution to resolve the issue. Most of the solutions are mentioned in the below link in the math section
https://docs.gitlab.com/ee/user/markdown.html
To summarise
This math is inline $`a^2+b^2=c^2`$
This is on a separate line
```math
a^2+b^2=c^2
```
Separate line with equation number
```math
\tag{1} a^2+b^2=c^2
```
Now, I am trying to find how to add \label{} in the equation.

Print formatted mathematical operations in R

I have in R a mathematical operation like this:
x = 5
y = (x / 5) * 2
and I want to print y to console or pdf file so it looks like:
(x / 5) * 2 like on the paper
Can I do this using R basic functions or some kind of library?
#Yehor: you can use the power of RStudio and RMarkdown to combine text, code, and visualisations in output formats like pdf. Under the hood you need a bit more than "some kind of library". But if you use RStudio as your R editor, the infrastructure (what you need) is actually in place already. RStudio will ask to have a few packages installed when you open a RMarkdown file for the first time, but do not worry about this.
In RStudio open a new RMarkdown file. During the opening dialogue you can (pre-)select an output type, e.g. pdf. Please note that you can change this later.
The example that opens gives you an idea of what you can do. The magic happens when you hit the "knit-button" in the top bar of the editor pane. R/RStudio will render the document and interpret code-chunks. These chunks can include "just" code, code to produce tables and/or graphics.
For math & formulae, RMarkdown supports 2 ways of presenting LATEX:
inline equation
equation mode
(I) inline equation - within single dollar signs $
You can include an inline equation anywhere in the text part of the Rmd document. For example:
This is how I add a formula: $y := \frac{x}{5} * 2$ within a line using inline code.
(II) equation mode - statement within double dollar signs $$
For the equation mode use $$ and have this on a separate line in Rmd.
$$y := \frac{x}{5} * 2$$
Knitting the Rmd in RStudio renders the document into a pdf (you can also export to html, MS Word or even Powerpoint).
For example:
is produced with this minimal Rmd:
If you want to combine this with the calculation, you would add a "code-chunk".
In RMarkdown you can include R-code inside 3 backticks, e.g. {r} # R-stuff ...
Thus, the following code chunks performs the operation:
x <- 5
y <- (x/5) * 2
If you want to print the result "inline" in your text, you can add so-called inline code. This is done by having R-statement inside single backticks and a starting r, i.e. r ... within the text part of the Rmd. For example:
My result is `r y` as inline code.
This will print: My result is 2 as inline code.
You could include more sophisticated R-statements as inline code by separating each statement with a semi-colon (~end of command line). However, I recommend to do the fluffy stuff in a code chunk and use the inline for simple statements. It is much easier on the eye and for debugging.

How can I write a degree symbol in RMarkdown 2?

I'm writing some code with descriptions using Rmarkdown 2 and knit PDF.
I've been trying many method to write a degree symbol inline:
Latex package: siunitx's \ang
Latex package: textcomp's \textdegree
Latex: \circ
And many possible RMarkdown symbols, such as:
$$ \textdegree $$ or $\textdegree$
But nothing is working. Is there a way to write a degree symbol in RMarkdown 2 and convert it do PDF?
EDIT (18 AUGUST 2014):
Ok, I found out where is the problem. If you use \circ in normal sentence or first-level list it is ok. But when I try to use \circ in second-level list - it's not working.
The problem was with RMarkdown converting nested lists. On this page http://rmarkdown.rstudio.com/authoring_pandoc_markdown.html you can find sentence:
The nested list must be indented four spaces or one tab
Although, using the tab could be a problem. When using four spaces - it works:
* Let's turn this round 360$^\circ$
+ Let's turn this round 360$^\circ$
Using \circ works for me, RStudio, knit to pdf:
Let's turn this round 360$^\circ$
You can use plotmath's degree, e.g.
plot(1, xlab=expression(4*degree))

equation not well formatted using markdownToHTML

Having this code in a test.md file
$$
\begin{aligned}
20x 1 \leqt 70
\end{aligned}
$$
When I use RStudio button Preview Html the equation is well formatted using Mathjax.
But when I try to do it using markdownToHTML function:
for example
markdownToHTML('test.md', 'test.html'),
the equation is not formatted.
The bug is due to the extra blank line after my equation( I can't remove it because the equation is generated using an R chunk and the cat command)
Does Rstudio does any post-processing on .md files to remove blank lines between $$ ?
For RStudio, we actually have our own version of the markdown package embedded which does the conversion from .md to .html. I tried your scenario and was able to reproduce as well. I recommend reporting this to Jeff Horner to see if there is a bug here that he can fix:
http://cran.r-project.org/web/packages/markdown/index.html
https://github.com/rstudio/markdown
Josh
Product Manager - RStudio

LaTeX Page Size --- how do I produce a page that is "just big enough"?

I was learning about using the command line version of latex today, and I was experimenting with outputting .tex to .dvi, and then .dvi to .png.
The problem is, I have a simple .tex document which contains some math. The goal is to eventually produce a png form of the equation. But when I run:
$ latex -output-format=dvi test.tex
$ dvipng test.dvi
I get test1.png that is shaped like a regular letter-sized page. I only want an image that is as big as the equation needs to be. I'm sure I'm missing something obvious, but I can't figure it out!
Is there a command line option for either latex or dvipng to specify that the output file should only be set on a page as large as needed to render the equation?
Here's my example test.tex:
\documentclass{article}
\begin{document}
The solution to $\sqrt{x} = 5$ is $x=25$.
\end{document}
Thanks!
Try
dvipng -T tight filename
EDIT: As Mr tur1ing points out, you'll also want \pagestyle{empty} to avoid having a page number muck up the works.
Try mathurl and Roger's Online Equation Editor. There probably several other such sites.

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