Matlab - Matrix

A Matrix is a two-dimensional array of elements. In MATLAB (short for Matrix Laboratory), the matrix is created by assigning the array elements that are delimited by spaces or commas and using semicolons to mark the end of each row.

Creating a Matrix in MATLAB

A matrix can be created by listing elements inside square brackets [ ].

• Elements in a row are separated by spaces or commas (,).
• Rows are separated by semicolons (;).

Syntax:

A = [elements; elements]

Example: Creating a Matrix

Output:

x =

1 2 3

4 5 6

7 8 9

y =

Geeks

Geeks

Finding the Size of a Matrix

You can find the dimensions (rows × columns) of a matrix using the size() function.

Example:

Output:

xSize =

3 4

ySize =

2 5

Accessing Matrix Elements

To access specific elements, use the syntax:

matrix(row, column)

Example 1: Access a Single Element

Output:

ans =

8

Example 2: Accessing Multiple Elements

To access multiple elements:

• x(:, :) -> all rows and columns
• x(1:2, :) -> first two rows
• x(:, 2:end) -> all rows, columns from 2 to end

Output:

ans =

1 2 3 4

4 5 6 7

7 8 9 10

ans =

1 2 3 4

4 5 6 7

ans =

2 3 4

5 6 7

8 9 10

ans =

2 3

5 6

Adding Elements or Dimensions

You can add rows or columns to a matrix using concatenation ([]) or the cat() function.

Syntax:

cat(dimension, A, B, ...)

• dimension = 1 -> adds rows
• dimension = 2 -> adds columns

Example 1: Using Brackets

Output:

a =

1 2 3 4

4 5 6 7

7 8 9 10

11 12 13 14

b =

1 2 3 4

4 5 6 7

11 12 13 14

x =

1 2 3 4 15

4 5 6 7 16

Example 2: Using cat()

Output:

a =

1 2 3 4

4 5 6 7

1 2 3 4

4 5 6 7

b =

1 2 3 4 1 2 3 4

4 5 6 7 4 5 6 7

Deleting Rows or Columns

You can remove rows or columns by assigning them an empty array [].

Example:

Key Points

• MATLAB indices start at 1 (not 0).
• For most operations, matrices must have the same dimensions.
• Use a semicolon (;) at the end of a statement to suppress intermediate outputs.
• In MATLAB, a string is treated as a character array.
• length() gives the total number of elements in a vector, while size() returns matrix dimensions.