How to write FOR LOOP in Matlab?

Hi;

Could you please explain below code? I study on for loop in Matlab to learn. I use generally tutorials from the Internet. I have seen below code in the Internet. But I could not understand what that code means.

A = [ [1 2 3]' [3 2 1]' [2 1 3]']

A =

       1     3     2
       2     2     1
       3     1     3

for j=2:3,

    A(j,:) = A(j,:) - A(j-1,:)

end

For example; What does "for j=2:3," row means?

What does "A(j,:) = A(j,:) - A(j-1,:)" means? I couldn't understand that as well.. Could you help me?

[the cyclist]

You might want to start with some very basic tutorials. For example, take a look at this page.

Answer 1

[the cyclist]

The code

for j=2:3,
    A(j,:) = A(j,:) - A(j-1,:)
end

means that you will run the middle line of code substituting the value j=2, and then you will run it substituting the value j=3.

So, it is the same thing as running the two lines of code

A(2,:) = A(2,:) - A(2-1,:)
A(3,:) = A(3,:) - A(3-1,:)

which is the same as

A(2,:) = A(2,:) - A(1,:)
A(3,:) = A(3,:) - A(2,:)

The colons in the second argument mean "do this for the whole row". It is a vector operation.

Answer 2

[Meghana Dinesh]

[1 2 3]' means transpose of [1 2 3] so it becomes:

[1
 2
 3]

This is the first column of A Similarly, you get [3 2 1]' and [2 1 3]' to get the second and third columns of matrix

for j=2:3,

means "for j equal to 2, till 3, in steps of 1 (by default, it is in steps of 1). So j takes the values 2 and 3.

A(j,:)

Here, j takes the values 2 and 3. The syntax is: A(1st dimension,2nd dimension). The 1st dimension is row, 2nd dimension is column. So the row of A takes the value 2 in the first iteration and 3 in the second iteration.

Example: A(2,:) means 2nd row of A and all columns. So, in the A matrix defined above, you will get

A(2,:) = [2 2 1]