# cat

stacks vectors matrices or arrays into an hypermatrix or hyperarray

### Syntax

`y = cat(dim, A1, A2, ...,An)`

### Arguments

dim

integer>0: index of the dimension along which input arrays must be stacked.

A1, A2,..An

scalars, vectors, matrices or hypermatrices of the same data type, or cells arrays. `A1,A2,...,An` must be of the same sizes, except in the direction #`dim` of stacking : `size(A1,i)=size(A2,i)=...=size(An,i)` for all `i <> dim`.

y

a vector, matrix, hypermatrix of A1's data type, or an hypercell. For all `i <> dim`, `size(y,i)==size(A1,i)`, and `size(y,dim) == sum(size(Ai, dim)))`.

### Description

`y=cat(dim,A1,A2,...,An)` : `y` is the result of the concatenation of the input arguments `A1,A2,...,An`, along the dimension #dim.

`cat(1, A1, A2, A3)` is equivalent to `[A1 ; A2 ; A3]`. `cat(2, A1, A2, A3)` is equivalent to `[A1 A2 A3]`. Brackets are faster and must be preferred in both cases.

`cat()` is useful mainly for `dim > 2`, to build an hypermatrix or hypercell.

### Examples

Example #1: Building a vector along dim #3

`cat(3, 4, -1, 3)`
```--> cat(3, 4, -1, 3)
ans  =
(:,:,1)
4.
(:,:,2)
-1.
(:,:,3)
3.
```

Example #2: Building a matrix of text of size(1,3,2):

`cat(3, ["a" "aa" "aaa"], ["b" "bb" "bbb"])`
```--> cat(3, ["a" "aa" "aaa"], ["b" "bb" "bbb"])
ans  =
(:,:,1)
!a  aa  aaa  !
(:,:,2)
!b  bb  bbb  !
```

Example #3: Stacking separate R G B layers of a mini RGB image:

```R = uint8(grand(2,4,"uin",0,255))
G = uint8(grand(2,4,"uin",0,255))
B = uint8(grand(2,4,"uin",0,255))
cat(3, R, G, B)```
```--> R = uint8(grand(2,4,"uin",0,255))
R  =
142    8   11  234
191  249  252   51

--> G = uint8(grand(2,4,"uin",0,255))
G  =
255  246  104  89
152   71  112  17

--> B = uint8(grand(2,4,"uin",0,255))
B  =
170  182  39  197
115  108  16   51

--> cat(3, R, G, B)
ans  =
(:,:,1)
142    8   11  234
191  249  252   51
(:,:,2)
255  246  104  89
152   71  112  17
(:,:,3)
170  182  39  197
115  108  16   51
```

Example #4: Building an hypercell:

```A1 = {%T   "abc" ; (1-%z)^2,  %pi}
A2 = {%s^2, gda(); %F, list(-5, "hello")}
cat(3, A1, A2)```
```--> A1 = {%T   "abc" ; (1-%z)^2,  %pi}
A1  =
[1x1 boolean   ]  [1x1 string  ]
[1x1 polynomial]  [1x1 constant]

--> A2 = {%s^2, gda(); %F, list(-5, "hello")}
A2  =
[1x1 polynomial]  [1x1 handle]
[1x1 boolean   ]  [    list  ]

--> cat(3, A1, A2)
ans  =
(:,:,1)
[1x1 boolean   ]  [1x1 string  ]
[1x1 polynomial]  [1x1 constant]

(:,:,2)
[1x1 polynomial]  [1x1 handle]
[1x1 boolean   ]  [    list  ]
```