Next: Indexing Cell Arrays, Up: Cell Arrays

#### 6.2.1 Creating Cell Array

The introductory example showed how to create a cell array containing currently available variables. In many situations, however, it is useful to create a cell array and then fill it with data.

The `cell` function returns a cell array of a given size, containing empty matrices. This function works very similar to the `zeros` function for creating new numerical arrays. The following example creates a 2-by-2 cell array containing empty matrices

         c = cell(2,2)
              => c =

                  {
                    [1,1] = [](0x0)
                    [2,1] = [](0x0)
                    [1,2] = [](0x0)
                    [2,2] = [](0x0)
                  }

Just like numerical arrays, cell arrays can be multidimensional. The `cell` function accepts any number of positive integers to describe the size of the returned cell array. It is also possible to set the size of the cell array through a vector of positive integers. In the following example two cell arrays of equal size is created, and the size of the first one is displayed

         c1 = cell(3, 4, 5);
         c2 = cell( [3, 4, 5] );
         size(c1)
              => ans =
                  3   4   5

As can be seen, the `size` function also works for cell arrays. As do the other functions describing the size of an object, such as `length`, `numel`, `rows`, and `columns`.

An alternative to creating empty cell arrays, and then filling them, it is possible to convert numerical arrays into cell arrays using the `num2cell` and `mat2cell` functions.

— Built-in Function: cell (x)
— Built-in Function: cell (n, m)

> Create a new cell array object. If invoked with a single scalar argument, `cell` returns a square cell array with the dimension specified. If you supply two scalar arguments, `cell` takes them to be the number of rows and columns. If given a vector with two elements, `cell` uses the values of the elements as the number of rows and columns, respectively.

— Built-in Function: iscell (x)

> Return true if x is a cell array object. Otherwise, return false.

— Loadable Function: c = num2cell (m)
— Loadable Function: c = num2cell (m, d)

> Convert to matrix m into a cell array. If d is defined the value c is of dimension 1 in this dimension and the elements of m are placed in slices in c.

> See also: mat2cell.

— Loadable Function: b = mat2cell (a, m, n)
— Loadable Function: b = mat2cell (a, d1, d2, ...)
— Loadable Function: b = mat2cell (a, r)

> Converts the matrix a to a cell array If a is 2-D, then it is required that `sum (`m`) == size (`a`, 1)` and `sum (`n`) == size (`a`, 2)`. Similarly, if a is a multi-dimensional and the number of dimensional arguments is equal to the dimensions of a, then it is required that `sum (`di`) == size (`a`, i)`.

> Given a single dimensional argument r, the other dimensional arguments are assumed to equal `size (`a`,`i`)`.

> An example of the use of mat2cell is

>               mat2cell (reshape(1:16,4,4),[3,1],[3,1])
>               => {
>                 [1,1] =

>                    1   5   9
>                    2   6  10
>                    3   7  11

>                 [2,1] =

>                    4   8  12

>                 [1,2] =

>                   13
>                   14
>                   15

>                 [2,2] = 16
>               }

> See also: num2cell, cell2mat.