# colon (:)

Ranging operator. Addresses all elements along an array dimension or of a list.

### Description

Colon symbol `:`

can be used to form implicit
vectors (see also linspace, logspace) :

- j:k
is the vector

`[j, j+1,...,k]`

(empty if`j>k`

);- j:d:k
is the vector

`[j, j+d, ..., j+m*d]`

.

The colon notation can also be used to pick out selected rows, columns and elements of vectors and other arrays (see also extraction, insertion):

- A(:)
is the vector of all the elements of

`A`

regarded as a single column;- A(:,j)
is the

`j`

-th column of`A`

;- A(i,:)
is the

`i`

-th row of`A`

;- A(j:k)
is

`[A(j),A(j+1),...,A(k)]`

;- A(:,j:k)
is

if size of[A(1,j) A(1,j+1) ... A(1,k) A(2,j) A(2,j+1) ... A(2,k) . . . . . . . . . . . A(M,j) A(M,j+1) ... A(M,k)]

`A`

is`M`

-by-`N`

;- A(j:k,:)
is

if size of[A(j,1) A(j,2) ... A(j,N) A(j+1,1) A(j+1,2) ... A(j+1,N) . . . . . . . . . . . A(k,1) A(k,2) ... A(k,N)]

`A`

is`M`

-by-`N`

;- A(:)=w
fills the array

`A`

with entries of`w`

(taken column by column if`w`

is a 2D array). The amount of entries of`A`

must be equal to the amount of entries of`w`

.

Please note that even if `i`

, `j`

,
`k`

or `d`

have a decimal part, only
the integer part will be used.

`type(:)` is 129.
`typeof(:)` is `"implicitlist"` . |

### Examples

a = 1:5 b = 1:3:12 A = matrix(1:42,7,6); // vector of all the elements of A A(:) // the j-th column of A A(:,j) // the i-th row of A A(i,:) // elements of columns from j to k and all rows A(:,j:k) // elements of all columns and rows from j to k A(j:k,:) w = matrix(101:142,7,6); A(:) = w // if indices are not integer i = 1:0.4:10; //indices A(i)

### See also

- dollar — ($) last index
- extraction — matrix and list entry extraction
- matrix — reshapes an array with the same number and order of components
- linspace — generates linearly spaced numbers between 2 reached bounds
- logspace — logarithmically spaced vector

### History

Version | Description |

6.0 | `%i:10` now yields an error. |

## Comments

Add a comment:Please login to comment this page.