MATLAB - Array Functions

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Array functions are a fundamental aspect of MATLAB, as they allow you to perform operations on arrays (also known as matrices) efficiently.

Let us take a look at all these array functions listed below with explanation and examples.

Function Name : zeros()

This function is used to create a matrix or array with all zeros.

Syntax

Z = zeros(n)

Using the function zeros(n) will return the nxn matrix with all zeros.

Example

A = zeros(3)

On execution you will get following output −

A =

     0     0     0
     0     0     0
     0     0     0

You can also specify the size you want , for example zeros(4,2) and the output will be −

ans =

     0     0
     0     0
     0     0
     0     0

Function Name: ones()

You will get an array or matrix with all ones.

Syntax

A = ones(n)
A = ones(sz1szN)

ones(n) will create a matrix of nxn size. ones(sz1sz1n) will create a matrix of size sz1xszn.

Example

A = ones(4)

When you execute the same in matlab command window the output is −

A =

     1     1     1     1
     1     1     1     1
     1     1     1     1
     1     1     1     1

Let us create matrix with ones of dimension 3x2 as shown below −

A = ones(3,2)

When you execute the same in matlab command window the output is −

A =
     1     1
     1     1
     1     1 

Function Name: eye()

You will get an identity matrix with the above function.

Syntax

I = eye(n)
I = eye(n,m)

With eye(n) you will get an nxn matrix and with eye(n,m) you get a matrix of size nxm.

Example

I = eye(4)
I = eye(2, 3)

When you check the output is matlab command window the output is −

I =
 Diagonal Matrix
 
     1     0     0     0
     0     1     0     0
     0     0     1     0
     0     0     0     1

I =
 Diagonal Matrix
 
     1     0     0
     0     1     0

Function name : rand()

Matrix with random numbers is generated with the above function.

Syntax

rand(n)
rand(sz1szn)

You can create a matrix of random numbers of size n or size sz1xszn.

Example

A = rand(4)
A = rand(5,3)

When you execute them in matlab command window the output is −

A =

    0.8147    0.6324    0.9575    0.9572
    0.9058    0.0975    0.9649    0.4854
    0.1270    0.2785    0.1576    0.8003
    0.9134    0.5469    0.9706    0.1419

A =

    0.4218    0.0357    0.7431
    0.9157    0.8491    0.3922
    0.7922    0.9340    0.6555
    0.9595    0.6787    0.1712
    0.6557    0.7577    0.7060

Function name : randn()

Matrices with random numbers that are normally distributed are generated using the above function.

Syntax

randn(n)
randn(sz1szn)

You can create a matrix of random numbers of size n or size sz1xszn.

Example

A = randn(4)
A = randn(5,3)

When you execute them in matlab command window the output is −

A =

   -1.1471    1.4384   -1.7115    0.3129
   -1.0689    0.3252   -0.1022   -0.8649
   -0.8095   -0.7549   -0.2414   -0.0301
   -2.9443    1.3703    0.3192   -0.1649

A =

    0.6277   -1.2141    0.3714
    1.0933   -1.1135   -0.2256
    1.1093   -0.0068    1.1174
   -0.8637    1.5326   -1.0891
    0.0774   -0.7697    0.0326 

Function name: size()

This method returns the size of the array or matrix.

Syntax

size(A)

Here A is a matrix and the function size() will return the dimensions of A in the form of row vector.

Example

A = [1,2,3;4,5,6;7,8,9]
size(A)

When you execute the above in the matlab command window the output is −

A =

     1     2     3
     4     5     6
     7     8     9

ans =

     3     3

Function name: reshape()

This function will reshape the array with the size given.

Syntax

B = reshape(A,sz)

Here sz is the size of the vector i.e [3,2] and matrix A will be reshaped to the size given.

Example

A = 1:8
B = reshape(A,[4,2])

When you check the output in matlab the output is −

A =

     1     2     3     4     5     6     7     8

B =

     1     5
     2     6
     3     7
     4     8

Function name: transpose()

This function will return the transpose of the given matrix or vector.

The output will have rows and columns interchanged when the transpose is done.

Syntax

B = transpose(A)

Example

A = magic(3)
B = transpose(A)

The output for above is −

A =

     8     1     6
     3     5     7
     4     9     2

B =

     8     3     4
     1     5     9
     6     7     2 

Function name : max()

This will give the maximum elements of an array as follows.

If the given input is a row vector , the maximum element from the row vector is given.

If the given input is a matrix, the row vector having the maximum element is given.

Syntax

B = max(A)

Here A is an array or matrix or a row vector.

Example 1

A = [23, 84, 36, 1, 20]
B = max(A)

When you execute in matlab command window the output is −

A =

    23    84    36     1    20

B = 84

Now let us take a matrix and find the max element using max().

Example 2

A = [56, 23, 90; 101, 45, 22;78, 11,90]
B = max(A)

When you execute above in matlab command window the output is −

A =

    56    23    90
   101    45    22
    78    11    90

B =

   101    45    90

Function name : min()

This will give the minimum elements of an array as follows.

If the given input is a row vector , the minimum element from the row vector is given.

If the given input is a matrix, the row vector having the minimum element is given.

Syntax

B = min(A)

Here A is an array or matrix or a row vector.

Example 1

A = [23, 84, 36, 1, 20]
B = min(A)

When you execute in matlab command window the output is −

A =

    23    84    36     1    20

B = 1

Now let us take a matrix and find the minimum element using min().

Example 2

A = [56, 23, 90; 101, 45, 22;78, 11,90]
B = min(A)

When you execute above in matlab command window the output is −

A =

    56    23    90
   101    45    22
    78    11    90

B =

    56    11    22

Function name: sum()

This method will return the sum of elements for a row vector or matrix.

If a row vector , it will return the sum of all the elements in the row vector.

If matrix, it will sum of all the columns and return row vectors.

Syntax

S = sum(A)

Here A is an array or matrix or a row vector.

Example 1

S = [2, 3, 80, 90, 12]
sum(S)

When you execute the output is −

S =

   2     3    80    90    12

ans = 187

Example 2

Now let us make use of the matrix as shown below and calculate the sum of it.

A = [1, 2,3;4,5,6;7,8,9]
S = sum(A)

When you execute the output is −

A =

     1     2     3
     4     5     6
     7     8     9

S =

    12    15    18

Function Name : mean()

This function will give the average or mean for the given array.

Syntax

M = mean(A)

If the given input is a row vector, then mean(A) will give you the mean of the elements.

If the given input is a matrix, then mean(A) will return a row vector which will have the mean of each of the columns.

Example 1

A = [23, 90, 33, 78, 11, 56]
M = mean(A)

When you execute the output will be −

A =

    23    90    33    78    11    56

M = 48.5000

Example 2

A = [51, 34 , 33; 12, 90, 32; 8, 13, 67]
M = mean(A)

In above example A is a 3x3 matrix. Now when you find out the mean(A) it will find the mean across each column and return a row vector.

On execution in matlab command window the output is −

A =

    51    34    33
    12    90    32
     8    13    67

M =

   23.6667   45.6667   44.0000

Function name : diag()

This method creates a diagonal matrix for the with the given vector row elements on the main diagonal.

Syntax

D = diag(v)

Here v is a row vector.

Example

v = [5 2 -1 -2 -5]
D = diag(v)

When you execute the same in matlab command window the output is −

v =

     5     2    -1    -2    -5

D =

  Diagonal Matrix

     5     0     0     0     0
     0     2     0     0     0
     0     0    -1     0     0
     0     0     0    -2     0
     0     0     0     0    -5

Function name: unique()

This method will return unique values in an array.

Syntax

C = unique(A)
C = unique(A, setOrder)

You will get an array C in sorted form , with no repetitions of the same values.

The second syntax you have to pass the setOrder, the values for it are : sorted or stable. By default the setOrder is sorted. If you want the final output not to be sorted you can mention it as 'stable'.

Example 1

A = [10, 8, 2, 4,8, 3]
C = unique(A)

When you execute the same in matlab command window the output is −

A =

    10     8     2     4     8     3

C =

     2     3     4     8    10

You will see that the value 8 is appearing twice in array A. When you see the output of unique(A), the repeated values are removed and the final array is in sorted form.

Example 2

Will use the same example we have used above and use the setOrder as stable.

A = [10, 8, 2, 4,8, 3]
C = unique(A, 'stable')

When you execute the same the output is −

A =

    10     8     2     4     8     3

C =

    10     8     2     4     3

Example 3

In case you give the matrix with duplicate values, the unique() method returns the columns vector with unique values as shown below.

A = [1,2,4; 4,2,8; 8,1,5]

C = unique(A)

When you execute the above in matlab command window the output is −

A =

     1     2     4
     4     2     8
     8     1     5

C =

     1
     2
     4
     5
     8

The result C is a single column vector containing the unique values from A.

Function name: sort()

This method will sort the array elements.

Syntax

B = sort(A)
B = sort(A, direction)

The syntax sort(A) will sort the elements of the array in ascending order.

The second syntax sort(A, direction) , here direction takes values ascend and descend.By default it is ascending order.

If the given input A is a vector, then sort(A) will sort the elements in the vector.

If the given input A is a matrix , then sort(A) will sort each column of the matrix.

Example 1

A = [6 -1 -7 2 3 8 -10 11 2]
B = sort(A)

When you execute the same in matlab command window the output is −

A =

     6    -1    -7     2     3     8   -10    11     2

B =

   -10    -7    -1     2     2     3     6     8    11

Example 2

In this example let us take a matrix and use sort on it.

A = [ -1, 7, 10; 3, -9, 2; 8, -2, -3]
B = sort(A)

When you execute the same in matlab command window the output is −

A =

    -1     7    10
     3    -9     2
     8    -2    -3

B =

    -1    -9    -3
     3    -2     2
     8     7    10

In the above example let us use the direction as descend.

A = [ -1, 7, 10; 3, -9, 2; 8, -2, -3]
B = sort(A, 'descend')

When you execute the same in matlab command window the output is −

A =

    -1     7    10
     3    -9     2
     8    -2    -3

B =

     8     7    10
     3    -2     2
    -1    -9    -3