Getting Started

Cell Arrays

Cell arrays in MATLAB are multidimensional arrays whose elements are copies of other arrays. A cell array of empty matrices can be created with the cell function. But, more often, cell arrays are created by enclosing a miscellaneous collection of things in curly braces, {}. The curly braces are also used with subscripts to access the contents of various cells. For example,

• C = {A sum(A) prod(prod(A))}
  

produces a 1-by-3 cell array. The three cells contain the magic square, the row vector of column sums, and the product of all its elements. When C is displayed, you see

• C = 
      [4x4 double]    [1x4 double]    [20922789888000]
  

This is because the first two cells are too large to print in this limited space, but the third cell contains only a single number, 16!, so there is room to print it.

Here are two important points to remember. First, to retrieve the contents of one of the cells, use subscripts in curly braces. For example, C{1} retrieves the magic square and C{3} is 16. Second, cell arrays contain copies of other arrays, not pointers to those arrays. If you subsequently change A, nothing happens to C.

You can use three-dimensional arrays to store a sequence of matrices of the same size. Cell arrays can be used to store a sequence of matrices of different sizes. For example,

• M = cell(8,1);
  for n = 1:8
     M{n} = magic(n);
  end
  M
  

produces a sequence of magic squares of different order.

• M = 
      [           1]
      [ 2x2  double]
      [ 3x3  double]
      [ 4x4  double]
      [ 5x5  double]
      [ 6x6  double]
      [ 7x7  double]
      [ 8x8  double]
  
  
  

You can retrieve the 4-by-4 magic square matrix with

• M{4}
  

Other Data Structures

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