How To Create A Submatrix In Matlab

mat2cell

Divide matrix into cell array of matrices

Syntax

c = mat2cell(x, m, n) c = mat2cell(x, d1, d2, d3, ..., dn) c = mat2cell(x, r)

Description

c = mat2cell(x, m, n) divides the two-dimensional matrix x into adjacent submatrices, each contained in a cell of the returned cell array c. Vectors m and n specify the number of rows and columns, respectively, to be assigned to the submatrices in c.

The example shown below divides a 60-by-50 matrix into six smaller matrices. MATLAB returns the new matrices in a 3-by-2 cell array:

mat2cell(x, [10 20 30], [25 25])

The sum of the element values in m must equal the total number of rows in x. And the sum of the element values in n must equal the number of columns in x.

The elements of m and n determine the size of each cell in c by satisfying the following formula for i = 1:length(m) and j = 1:length(n):

```
size(c{i,j}) == [m(i) n(j)]          
```

c = mat2cell(x, d1, d2, d3, ..., dn) divides the multidimensional array x and returns a multidimensional cell array of adjacent submatrices of x. Each of the vector arguments d1 through dn should sum to the respective dimension sizes of x such that, for p = 1:n,

```
size(x,p) == sum(dp)          
```

The elements of d1 through dn determine the size of each cell in c by satisfying the following formula for ip = 1:length(dp):

size(c{i1,i2,i3,...,in}) == [d1(i1) d2(i2) d3(i3) ... dn(in)]

If x is an empty array, mat2cell returns an empty cell array. This requires that all dn inputs that correspond to the zero dimensions of x be equal to [].

For example,

a = rand(3,0,4); c = mat2cell(a, [1 2], [], [2 1 1]);

c = mat2cell(x, r) divides an array x by returning a single-column cell array containing full rows of x. The sum of the element values in vector r must equal the number of rows of x.

The elements of r determine the size of each cell in c, subject to the following formula for i = 1:length(r):

```
size(c{i},1) == r(i)          
```

Remarks

mat2cell supports all array types.

Examples

Divide matrix X into 2-by-3 and 2-by-2 matrices contained in a cell array:

X = [1 2 3 4 5; 6 7 8 9 10; 11 12 13 14 15; 16 17 18 19 20] X =      1     2     3     4     5      6     7     8     9    10     11    12    13    14    15     16    17    18    19    20  C = mat2cell(X, [2 2], [3 2]) C =      [2x3 double]    [2x2 double]     [2x3 double]    [2x2 double]  C{1,1}                          C{1,2} ans =                           ans =      1     2     3                   4     5      6     7     8                   9    10  C{2,1}                          C{2,2} ans =                           ans =     11    12    13                  14    15     16    17    18                  19    20

See Also

cell2mat, num2cell