# Colon :

## Purpose

Create vectors, matrix subscripting, and `for` iterations.

## Description

The colon is one of the most useful operators in MATLAB. It can create vectors, subscript matrices, and specify `for` iterations.

The colon operator uses the following rules to create regularly spaced vectors:

    -------------------------------------------------------------------
    j:k    is the same as [j,j+1,...,k]
    j:k    is empty if j > k
    j:i:k  is the same as [j,j+i,j+2i, ...,k]
    j:i:k  is empty if i > 0 and j > k or if i < 0 and j < k
    -------------------------------------------------------------------

Below are the definitions that govern the use of the colon to pick out selected rows, columns, and elements of vectors and matrices:

    -------------------------------------------------------------------
    A(:,j)    is the j-th column of A
    A(i,:)    is the i-th row of A
    A(:,:)    is the same as A
    A(j:k)    is A(j), A(j+1),...,A(k)
    A(:,j:k)  is A(:,j), A(:,j+1),...,A(:,k)
    A(:)      is all the elements of A, regarded as a single column. On
              the left side of an assignment statement, A(:) fills A,
              preserving its shape from before.
    -------------------------------------------------------------------

## Examples

Using the colon with integers,

    D = 1:4

results in

    D =
        1    2    3    4

Using two colons to create a vector with arbitrary real increments between the elements,

    E = 0:.1:.5

results in

    E =
        0    0.1000    0.2000    0.3000    0.4000    0.5000

## See Also

    for, linspace, logspace, reshape

(c) Copyright 1994 by The MathWorks, Inc.