Xy-pic User's Guide

## 1.2 Entries

A diagram is created by the command

`\xymatrix``{` ... `}`

where the "..." should be replaced by entries to be aligned in rows and columns where

- entries in a row are separated by `&` and
- entire rows are separated by `\\`.

For example,

was typeset by

>     \xymatrix{
>       A &*+[F]{\sum_{i=n}^m {i^2}} \\
>         & {\bullet} & D \ar[ul]     }

Notice the following:

- entries are typeset as mathematics (using "text style"); entries should not start with a macro (as illustrated by the use of `{}` around `\bullet`.
- all entries are centered,
- the separation between rows and columns is usually quite large in a diagram,
- empty entries at the end of rows may be omitted,
- "Xy-decorations" (here `\ar[ul]`) in entries allow drawing of arrows and such relative to the entries without changing the overall layout, and
- "Xy-modifiers" (here `*+[F]`) first in entries allow changing the format and shape in many ways.

Xy-pic User's Guide