LaTeX

Within R markdown (within RStudio), we can use the LaTeX language to create beautiful mathematical equations. Here are some examples to work through.


The helpful $ and $$
If I type $f_X(x)$ in a body of text, it produces fX(x). Notice that this LaTeX text is started by $ and ended by $. With just 1 $ on either end, the formula remains in my body of text. If I want it to appear on its own in the center of the page I use $$ on either end. For example, $$f_X(x)$$ gives fX(x)


Basic features

  • probability & counting stuff

    code result
    $P(A)$ P(A)
    $P(A \cap B)$ P(A∩B)
    $P(A \cup B)$ P(A∪B)
    $P(A|B)$ P(A|B)
    ${n \choose x}$ (nx)

  • subscripts

    code result
    $x_2$ x2
    $x_10$ x10
    $x_{10}$ x10

  • superscripts

    code result
    $x^2$ x2
    $x^10$ x10
    $x^{10}$ x10

  • fractions

    code result
    $\frac{1}{2}$ 12
    $\frac{a+1}{b+0}$ a+1b+0

  • integrals

    code result
    $\int f(x) dx$ ∫f(x)dx
    $\int_0^1 f(x) dx$ ∫10f(x)dx
    $\int_{-1}^{10} f(x) dx$ ∫10−1f(x)dx
    $\int_{-\infty}^\infty f(x) dx$ ∫∞−∞f(x)dx


Multi-line equations

One of many ways to present a multi-line equations is by using split. In the examples below, notice the following:

  • start with \begin{split} and end with \end{split}
  • indicate the end of each line in the equation by \\
  • use & to indicate the point at which to line up the lines


This code

$$\begin{split}
x & = 1 \\
y & = 2 \\
\end{split}$$

produces

x=1y=2

This code

$$\begin{split}
P(A|B) & = \frac{P(A \cap B)}{P(B)} \\
       & = \frac{P(B|A)P(A)}{P(B)} \\
\end{split}$$

produces

P(A|B)=P(A∩B)P(B)=P(B|A)P(A)P(B)

“Cases” are special type of multi-line equation:

$$f(x) = \begin{cases}
 0.2 & x = 1 \\
 0.8 & x = 2 \\
\end{cases}$$

produces

f(x)={0.2x=10.8x=2