Typesetting LaTeX fraction terms to be larger in an equation

Question

I have the following formula in LaTeX, based on Fisher's Exact Test. (NOTE: requires the use of the amsmath package for \binom.)

\begin{equation}     P(i,j) = \sum_{x=|N(V_i) \cap V_j|}^{\min\{|V_j|, |N(V_i)|}     \frac{ \binom{|V_j|}{x} \binom{|V - V_j|}{|N(V_i)| - x}}     {\binom{|V|}{|N(V_i)|}} \end{equation} 

This renders the fraction portion with very small, difficult to read text:

I would like my text more readable, as in the following example:

equation with readable text in fraction http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0005313.e002&representation=PNG

What trickery can I use to get LaTeX to render my equation similarly?

Answer 1

This may be what you're looking for:

\begin{equation}     P(i,j) = \sum_{x=|N(V_i) \cap V_j|}^{\min\{|V_j|, |N(V_i)|}      \frac{\displaystyle \binom{|V_j|}{x} \binom{|V - V_j|}{|N(V_i)| - x}}     {\displaystyle \binom{|V|}{|N(V_i)|}}    \end{equation} 

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Thought it might be good to add a reference:

A Guide to LaTeX2e, Kopka & Daly, 1995
Section 5.5 Fine-Tuning Mathematics
5.5.2 Selecting font size in formulas

In my edition, it's on pp 141-142, but this is out of stock on Amazon. The nearest Internet pointer I can find just now is here

Answer 2

Here's one idea.

In Preamble:

\def\mathLarge#1{\mbox{\LARGE $#1$}} 

Then update your equation to:

\begin{equation}     P(i,j) = \sum_{x=|N(V_i) \cap V_j|}^{\min\{|V_j|, |N(V_i)|}       \mathLarge{         \frac{ \binom{|V_j|}{x} \binom{|V - V_j|}{|N(V_i)| - x}}         {\binom{|V|}{|N(V_i)|}}     } \end{equation} 

Results in:

Answer 3

For fraction you can also use continued fraction \cfrac in combination with \left and \right.

Take a look here>>

Answer 4

The following lines define three fraction commands with sizes intermediate between \displaystyle and \textstyle, in order of decreasing size:

\newcommand{\sdfrac}[2]{\mbox{\small$\displaystyle\frac{#1}{#2}$}} \newcommand{\fdfrac}[2]{\mbox{\footnotesize$\displaystyle\frac{#1}{#2}$}} \newcommand{\ltfrac}[2]{\mbox{\large$\frac{#1}{#2}$}} 

See this page if further explanation is needed.