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Colon Notation Function using Matrices

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ssmith
ssmith on 16 Nov 2021
Answered: Awais Saeed on 16 Nov 2021
I have two matrices
A = [-1, 2, -3; 4, -5, 6]
B = [0, -1; 2, 10; -4, 3]
And I need help understanding what is happening in these functions:
A(2,2:3)
B(:2)
ans =
-5 6
ans =
-1
10
3

Answers (2)

the cyclist
the cyclist on 16 Nov 2021
Edited: the cyclist on 16 Nov 2021
A(2,2:3)
means "the 2nd row, 2nd-through-3rd column of A".
B(:,2)
means "all rows, 2nd column of B".
I strongly recommend the MATLAB Onramp tutorial. It covers basic MATLAB like this.

Awais Saeed
Awais Saeed on 16 Nov 2021
understand the syntax first. To access an element from a matrix, you need to provide the row and column in which it resides.
% for example
A = magic(4)
A(3,2) % access element at row = 3, column = 2
: operator means to select a range of rows or coloums
A(:, 2) % access column = 2 from all rows. Use : to select all rows at once
A(1, :) % access entire row = 1. Use : to select all columns at once
A(1:3, 2:3) % access row from 1 to 3 and column from 2 to 3

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