what does A(3, :) mean or A(:, 3)?

Question says it all

Answer 1

[James Tursa]

If A is a 2D matrix, then

A(3,:) is the 3rd row of A

A(:,3) is the 3rd column of A

If A is a multi-dimensional array, then a bit more explanation is required, which can be found here:

https://www.mathworks.com/help/matlab/ref/colon.html?searchHighlight=colon&s_tid=doc_srchtitle

[Vaibhav Giria]

thx

Answer 2

[Philip Abel]

Given a matrix "a" with elements

a = [1 2 3; 4 5 6]

To find a(x,y), it is important to note that:

• x stands for row
• y stands for column.
• : stands for all
• thus, a(x,y) is the element where x and y intersects.

1. a(1,3) : is the element on the intersection of row 1 and column 3.
2. a(:,3) : are the elements on the intersection of all rows and column 3.
3. a(1,:) : are the elements on the intersection of row 1 and all columns.

a = [1 2 3; 4 5 6];
p = a(1,3)

p = 3

q = a(:,3)

q = 2×1

3 6

r = a(1,:)

r = 1×3

1 2 3