Matrix

A matrix is a rectangular array of numbers. it can be created with elements included in a pair of square brackets. The rows are separated by semicolons, while elements in the same row are separated by commas.
>> A = [1,4, 9; 2, 3, 5; -2, 5, 10]
   1   4   9
   2   3   5
  -2  5    10
>>

Create Matrices

Alternatively, a matrix of a required size can be created and initialized using built-in functions zeros, ones, or rand. The command

A = zeros(3, 5)
will return a matrix of three rows and five columns, with each element being zero. Similar usage of ones and rand will create matrices of 1's and random numbers (between 0 and 1) respectively.

These three functions can also be called with a single parameter, in which case the second parameter is assumed to be 1, and thus a column vector is created.

>> B = rand(5)

    0.289    
    0.353    
    0.154    
    0.566    
    0.821
>>
By the dimension of a matrix we refer to the number of rows and the number of columns. For example, the dimension of the scalar -5 is , while the dimension of
   -2    3    9
    10   1    -2
is .

Create Even Spaced Vectors Using the Colon Operator

The symbol : can be used to create a row matrix whose elements are evenly spaced. The default step-size of the vector is 1, which is assumed when one colon is used.

>> A = -1 : 5
   -1  0  1  2  3   4   5
To specify a step-size other than 1, two colons are needed.
>> A = 3 : 0.5 : 5
   3  3.5  4  4.5  5

Scalar, vector, and matrix

Every numerical value is treated as a matrix. It is only for convenience that sometimes we call some special matrices scalars or vectors. There is no distinction between a scalar, a, row or column vector of length 1, or matrix. Likewise, a row vector of five elements is the same as a matrix, and a column vector of five elements is the same as a matrix.

oz 2009-12-22