[Tex/LaTex] Writing equation in LaTeX: some part are thesterious to me :)

equationsmath-mode

I would like to write in LaTeX two equations:

equation1

and

enter image description here

I do not know how to do that…Particularly, how to write stuff underneath the max function. And also how to have this line over Wi or Wj.

PS: I do not ask for the whole equations, I am asking for the part that I do not know how to write in LaTeX :))

Best Answer

In the case of \max, the text below automatically. For other operators (like \int) or for inline formulas, you can use \limits. Longer text has to be in curly brackets:

\max\limits_{n_j \in succ(n_i)}

To get a line over your text, you can use \overline:

\overline{w_i}

Your formulas would be:

rank_u(n_i) = \overline{w_i} + \max\limits_{n_j \in succ(n_i)} (\overline{c_{ij}} + rank_u(n_j))
rank_d(n_i) = \max\limits_{n_j \in pred(n_i)} \{rank_d(n_j) + \overline{w_j} + \overline{c_{i,j}}\}

If you want to typeset rank and succ as an operator like max, you can either use \text{rank} from amsmath, or declare rank as a math operator (in your preamble):

\DeclareMathOperator{\rank}{rank}
\DeclareMathOperator{\successor}{succ}

Please note that I chose \successor over \succ, as this is already used for a math symbol.

Related Solutions

[Tex/LaTex] how to write maximize over multiple conditions

You can use \substack, provided by the amsmath package:

\documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\begin{document}
\[
  \max_{0 \leq x \leq 1} f(x)
\]

\[
  \max_{\substack{0 \leq x \leq 1 \\ a \geq y \geq b}} f(x)
\]
\end{document}

Substack as limits

It works similar to an array where multiple lines are separated using \\. Another alternative would be to use the \mathop - it produces the same result as above:

\documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\begin{document}
\[
  \mathop{\max_{0 \leq x \leq 1}}_{a \geq y \geq b} f(x)
\]
\end{document}

\mathop makes it's argument an operator, which allows for the traditional limit placement using _ and/or ^ which adds it below/above the operator.

[Tex/LaTex] Writing readable LaTeX

Most of what I say is covered by other answers, but I will write here my thoughts.

First of all, if you write a lot in LaTeX format, I think you should leave LyX and go for any plain text editor. In the (near) future you will be faster (reading and writing code).

About writing readable code. Here are some tips to make it readable:

One of the main features I found in LaTeX is the ability you have to write what you want. But don't fail at deciding what you want! I mean, in your code you (shouldn't want) don't want x to be bold (mathbf), you must want x to be a vector (\vec{x}). You will decide later what a vector looks like, but at first, you don't have to worry about it.
Next, if you usually define some sets you can define \set command (and later you will worry about how sets are displayed), but, as David Carlisle pointed, you can define shorter commands.
This is a must have in my documents: \R (\mathbb{R}) to define the real numbers. It is an entity so I define a command to call them. But I wouldn't define \Rn for \mathbb{R}^n, because then you aren't writing what you want, you are fastening your code input (which shouldn't be done that way).
May be \quad is not easy readable for you, but I think it will in the future.
This example is no so long, so you can't see how indenting your code benefits the reading of your code, but it really does.
I use \[,\] but I don't use $ and $ because I don't read math really good between those delimiters. So I changed them to $.
Personally, I don't write comments in my code unless I need to edit it later or something (I use comments as reminders). If you read code fast you don't need comments which explains what are you doing (in my case, they break my concentration).

This is how I would write your code:

\documentclass{article}
\usepackage{mathtools}
\usepackage{amsfonts}

\renewcommand\vec[1]{\mathbf{#1}}
\newcommand\set[1]{\mathcal{#1}}
\newcommand\R{\mathbb{R}}

\begin{document}
\subsection{Convex sets}
A set $\set{S}$ in $\R^n$ is said to be convex if 
\[
    \vec{x}_1, \vec{x}_2 \in \set{S} \implies \lambda \vec{x}_1 + (1-\lambda) \vec{x}_2 \in \set{S} \quad \text{for all } 0 < \lambda < 1 
\]
\end{document}

After that, I think you should differentiate writing code and fastening your input. Most of people defines commands to write faster (like \newcommand\vx{\vec x} from Niel de Beaudrap). I don't agree with that. To write faster you should use an editor (or a third party app) which lets you create snippets (i.e. I would make a snippet with \vec{x} which would be called when you type vx).

At last, to fasten your code-reading you must use a program which shows your code with colors (a color for math, a color for commands, a color for text,…). This is an example of my code (the theme and font I show here is not the usual, but I'm not in my main operating system, however I don't hate this setup): enter image description here

Summary

These are my ideas:

Write what you want (but don't misunderstand what you really want). The commands you use have to be entities, not just 'shortcuts'. Later, you will care about how will it look like.
Don't use commands as snippets (use a good editor or a third party app to make use of snippets).
Indent your code.
Use an editor which displays the code with different colors.
Again, if you want your code to be readable don't use \mathbf{x} \in \mathbb{R}^n or \vx \in \Rn. I would go for \vec{x} \in \R^n.

Best Answer

Related Solutions

[Tex/LaTex] how to write maximize over multiple conditions

[Tex/LaTex] Writing readable LaTeX

Summary

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