# for

## Purpose

Repeat statements a specific number of times.

## Synopsis

````for variable = expression`
`    statements`
`end`
```

## Description

The general format is

````for variable = expression`
`    statement`
`    ...`
`    statement`
`end`
```
The columns of the `expression` are stored one at a time in the variable while the following statements, up to the `end`, are executed.

In practice, the `expression` is almost always of the form `scalar` : `scalar`, in which case its columns are simply scalars.

The scope of the `for` statement is always terminated with a matching `end`.

## Examples

Assume `n` has already been assigned a value. Create the Hilbert matrix, using `zeros` to preallocate the matrix to conserve memory:

````a = zeros(n,n)  % Preallocate matrix`
`for i = 1:n`
`    for j = 1:n`
`        a(i,j) = 1/(i+j -1);`
`    end`
`end`
```
Step `s` with increments of `-0.1`

````for s = 1.0: -0.1: 0.0,...,` `end`
```
Successively set `e` to the unit `n`-vectors:

````for e = eye(n),...,` `end`
```
The line

````for V = A,...,` `end`
```
has the same effect as

````for j = 1:n,` `V = A(:,j);..., end`
```
except `j` is also set here.

````break`, `end`, `if`, `return`, `while`