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    How to use Math tags

    A previous thread covered this topic (found here) but I figured a more detailed explanation could be given to help some people out.

    Contents
    1. How do I use math tags?
    2. Symbols
    3. Subscript/Superscript/Other Modifiers
    4. Fractions/Integration/Summation/Limits
    5. Tables
    6. Misc.

    0.5) Why math tags? Why not tex tags?

    The forum has both math and tex tags. However, the tex tags seem broken and don't properly render a lot
    of stuff so we *highly* suggest using math tags instead of trying to get tex tags to work.

    1) How do I use math tags?

    The forum includes typesetting using LaTex through the use of two special tags:
    [math] and [/math].

    A quick example - The following code:

    [math]Y_i = \mu_i + \epsilon_i[/math]

    produces the following result: Y_i = \mu_i + \epsilon_i

    There are various ways to see the code somebody else used to produce their mathematical typesetting. If you have javascript enabled you can click on their typesetting and a popup will display the code they used. If that doesn't work you can always 'quote' the post of interest and examine their post directly to see how they formatted it.

    2) Symbols

    There are many symbols that can be produced through the use of LaTeX. There are many guides on the internet that will show you the thousands of symbols that can be created. However, for a quick guide you can refer here or just browse other member's posts. It's not that bad and you can learn quickly. For a quick list of the more commonly used symbols you can refer below:

    \begin{tabular}{|l|c|}\hlineCode & Result \\\hlinealpha & $\alpha$ \\beta & $\beta$ \\epsilon & $\epsilon$ \\lambda & $\lambda$ \\mu & $\mu$ \\sigma & $\sigma$ \\theta & $\theta$ \\chi & $\chi$ \\\hline\end{tabular}
    \begin{tabular}{|l|c|}\hlineCode & Result \\\hlinecap & $\cap$ \\cup & $\cup$ \\cdot & $\cdot$ \\cdots & $\cdots$ \\ldots & $\ldots$ \\\hline\end{tabular}
    \begin{tabular}{|l|c|}\hlineCode & Result \\\hlineleq & $\leq$ \\geq & $\geq$ \\neq & $\neq$ \\subset & $\subset$ \\sim & $\sim$ \\equiv & $\equiv$ \\propto & $\propto$ \\\hline\end{tabular}
    \begin{tabular}{|l|c|}\hlineCode & Results \\\hlineexists & $\exists$ \\forall & $\forall$ \\infty & $\infty$ \\mathbb\{R\} & $\mathbb{R}$ \\mathbb\{N\} & $\mathbb{N}$ \\mathbb\{Z\} & $\mathbb{Z}$ \\\hline\end{tabular}

    and there are lots more. Note that you would need to add "\" to the front of any of that 'code' to produce the actual symbol inside of a math tag. That should give you a good start though. Note that you don't need a symbol to to a 'less-than' or 'greater-than' because you already have '<' and '>' on your keyboards.

    3) Subscript/Superscript/Other Modifiers

    If you want to add a superscript or subscript LaTeX makes it easy. The superscript operator is '^' and the subscript operator is '_'. For example
    HTML Code: 
    [math]x^2[/math]
    Produces x^2
    and
    HTML Code: 
    [math]x_i[/math]
    Produces x_i. It's possible to have both.
    HTML Code: 
    [math]x^2_i[/math]
    Produces x^2_i. If you want to have more than one character as part of your superscript or subscript you need to enclose the entire phrase in curly braces i.e.
    HTML Code: 
    [math]y^{3x - 5}_{max}[/math]
    Produces y^{3x - 5}_{max}.

    There are also other useful modifications one could want to make to symbols. A few of which are adding a bar, a hat, or making something bold. For example:

    HTML Code: 
    [math]\bar{x}[/math]
    Produces \bar{x}

    HTML Code: 
    [math]\hat{y}[/math]
    Produces \hat{y}

    and for when you work with vectors a lot of times you want to make something bold to let people know that it's a vector. We can do something like that by using \mathbf{}. For example:
    HTML Code: 
    [math]f(\mathbf{y} | \theta) = \prod_{i=1}^n f(y_i | \theta) [/math]
    gives f(\mathbf{y} | \theta) = \prod_{i=1}^n f(y_i | \theta)

    4) Fractions/Integration/Summation/Limits

    Fractions

    In LaTeX fractions have the same general form:
    HTML Code: 
    [math]\frac{numerator}{denominator} [/math]
    A few examples:
    HTML Code: 
    [math]\frac{7!}{2!(7-2)!}[/math]
    Produces \frac{7!}{2!(7-2)!}

    HTML Code: 
    [math] \frac{\beta^{\alpha}}{\Gamma (\alpha)} [/math]
    Produces \frac{\beta^{\alpha}}{\Gamma (\alpha)}

    Integration

    If you want to write out some formulas involving integration then \int is your friend.
    HTML Code: 
    [math] \int x^2 dx = \frac{1}{3}x^3 + c [/math]
    Produces \int x^2 dx = \frac{1}{3}x^3 + c. It's easy enough to add limits to the integration using the superscript and subscripts we used before. For example:

    HTML Code: 
    [math] \int_{-\infty}^{\infty} \frac{1}{\sqrt{2 \pi}}e^{-\frac{x^2}{2}} dx = 1 [/math]
    Produces \int_{-\infty}^{\infty} \frac{1}{\sqrt{2 \pi}}e^{-\frac{x^2}{2}} dx = 1

    Summation

    Our example will involve the binomial distribution:
    HTML Code: 
     [math] \sum_{x = 0}^n {n \choose{x}} p^x (1-p)^{n-x}  [/math]
    Produces \sum_{x = 0}^n {n \choose{x}} p^x (1-p)^{n-x}

    Limits
    Limits get their own subsection for the sole reason that not everybody realizes that \lim is a latex command. Notice the difference between the following two examples

    HTML Code: 
     [math] lim_{x \rightarrow \infty}[/math]
    [math] \lim_{x \rightarrow \infty}[/math]
    The first looks like this: lim_{x \rightarrow \infty} while the second looks much better: \lim_{x \rightarrow \infty}

    5) Tables

    When presenting data a lot of times it will look much nicer in tabular form. An example table:
    HTML Code: 
    [math]
    \begin{tabular}{|l|cr|}
    \hline
    ID & Age & Weight \\
    \hline
    Ted & 25 & 180 \\
    Frank & 52 & 169 \\
    Sue & 32 & 125 \\
    \hline
    \end{tabular}
    [/math]
    Which will produce:
    \begin{tabular}{|l|cr|}\hlineID & Age & Weight \\\hlineTed & 25 & 180 \\Frank & 52 & 169 \\Sue & 32 & 125 \\\hline\end{tabular}

    You must start a table with the \begin{tabular} command. The portion directly after that (it looks like {|l|cr|} ) is quite customizable. What that part does is control how many columns the table will have, where you will have vertical lines, and how each column is justified. By adding the pipe character (it looks like '|' and is obtained by holding shift and hitting the key above 'enter') you add a vertical line to separate columns. The different letters (l, c, r) stand for "left", "center", and "right" justified. The command \hline tells the table when to add a horizontal line. Once you get to the portion of the table where you're actually adding data you separate the data between columns with the '&' character. You tell the table that you are finished with a row by ending it with two backslashes ("\\"). When you're finished with the table you need the \end{tabular} command.

    Another example:
    HTML Code: 
    [math]
      \begin{tabular}{|c|c|c|}
        \hline
        Parameter &  Point Estimate & 95\% Interval Estimate \\
        \hline
        $\beta_0$ & .503752 & (0.35280, 0.65470) \\
        $\beta_1$ & .002229 & (0.00191, 0.00254) \\
        $\beta_2$ & -1.286 & (-2.5331, -.038942) \\
        \hline
      \end{tabular}
    [/math]
    \begin{tabular}{|c|c|c|}    \hline    Parameter &  Point Estimate & 95\% Interval Estimate \\    \hline    $\beta_0$ & .503752 & (0.35280, 0.65470) \\    $\beta_1$ & .002229 & (0.00191, 0.00254) \\    $\beta_2$ & -1.286 & (-2.5331, -.038942) \\    \hline  \end{tabular}

    If you use R and want to create a table from some data you might be interested in the xtable package. It will automatically generate the latex code to create a table from your data which can save you lots of time copying/pasting and inserting various symbols.

    End Remarks


    There is a lot more you can do with LaTeX that went unmentioned. Hopefully you have a decent understand how to use some of the basic math typesetting available to you here.

    Other references on how to use LaTeX:
    http://www.artofproblemsolving.com/W.../LaTeX:Symbols
    http://www.physicsforums.com/misc/howtolatex.pdf

    It should be noted that not all features of LaTeX are enabled in this web environment but you should be able to do almost anything you would want to post. If you have questions feel free to ask.
    Last edited by Dason; 02-20-2015 at 01:41 PM. Reason: Added: xbar, yhat, bold, and links!

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