Help On LaTeX arrays

# Hypertext Help with LaTeX
Arrays

     \begin{array}[pos]{vvvv}
     column 1 entry &: column 2 entry ... & column n entry \\
     ...
     ...
     ...
     \end{array}

The array environment, like the tabular environment, produces a box consisting of a sequence of rows of vertically aligned columns. It can be used only within the math environment.

There is a single mandatory argument describing the number of columns and the alignment within each of them. Each of the `v`'s in the argument specifies a column and may be a `l`, `c`, or `r` indicating that the column should be flush left, centered, or flush right, respectively. For more complex options, see the tabular environment which uses the same format.

The optional `pos` argument specifies the alignment of the array with its surrounding environment (recall that LaTeX treats boxes as one, albeit large letter). The options are

- `t` - align on top row
- `b` - align on bottom row

The default is to align on the center of the array.

Column entries must be separated by an `&`. Column entries may include other LaTeX commands, even other arrays. Each row of the array must be terminated with the string `\\`. Note that there is no `&` after the last item in a row and no `\\` after the last row. (An exception is if an `\hline` is used to place a line at the bottom; it follows a `\\`.)

Each item in the array is treated as if it were surrounded by braces. Thus, a declaration within an array item is local to that item, i.e., it is ended by an `&` or `\\`.

Horizontal and vertical lines in the array are produced with

- `\cline`
- `\hline`
- `\vline`

See also

- tabular environment
- math environment

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