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  ]

## See also

- brackets [..]
- lstcat
- permute
- matrix