Why math notation in R markdown?
- Math notation is the standard for technical descriptions of machine learning/statistical models.
- You may want to intersperse your technical decriptions with plain language descriptions.
- Math notation allows you to be precise
- “We fit a linear model with terms for age, sex” versus \( Y_i = \alpha + \beta_a A_i + \beta_s S_i + \epsilon_i \)
- Math notation allows you to be concise
- “We estimated the intercept to be 3.3” versus \( \hat{\alpha}=3.3 \).
What notation system does R markdown use?
- R markdown uses the same system as Latex
- The basic idea:
- You write your document in R markdown
- You include symbols for math notation
- You indicate math by wrapping the symbols with certain text
- Often the symbols are intuitive: \alpha gives you \( \alpha \)
How to write math inline
Including math in a sentence involves wrapping the symbols in $ symbols. For
example if you write this in an R markdown file:
“The intercept was estimated as $\hat{\alpha} = 4$”
Then you get the following text after running knit2html or slidify on your document.
“The intercept was estimated as \( \hat{\alpha} = 4 \)”
How to write math on a separate line
Sometimes you have several equations you would like to line up. The
way that you do that is with a double dollar sign \\[ and the align command.
For example if you write
Then you get the following text after running _knit2html_ or _slidify_ on your document.
\]
\begin{aligned}
y &= \beta_0 + \beta_1 + x_1 + \epsilon\
x &= \gamma z \
z &\sim N(0,1)
\end{aligned}
$$
Common symbols
- Subscripts to get \( a_{b} \) write:
$a_{b}$
- Superscripts write \( a^{b} \) write:
$a^{b}$
- Greek letters like \( \alpha, \beta, \ldots \) write:
$\alpha, \beta, \ldots$
- Sums like \( \sum_{n=1}^N \) write:
$\sum_{n=1}^N$
- Multiplication like \( \times \) write:
$\times$
- Products like \( \prod_{n=1}^N \) write:
$\prod_{n=1}^N$
- Inequalities like \( <, \leq, \geq \) write:
$<, \leq, \geq$
- Distributed like \( \sim \) write:
$\sim$
- Hats like \( \widehat{\alpha} \) write:
$\widehat{\alpha}$
- Averages like \( \bar{x} \) write:
$\bar{x}$
- Fractions like \( \frac{a}{b} \) write:
$\frac{a}{b}$
- Big parentheses like \( \left(\frac{a}{b}\right) \) write:
$\left(\frac{a}{b}\right)$
For more information
- Rstudio's equations page:
- Lists of Latex symbols