what is the meaning of A(:,:,1:2:3);

didnt get the meaning of 1:2:3 clearly.

[Stephen23]

Did you try it:

>> 1:2:3
ans =
 1   3

And read the documentation?:

https://www.mathworks.com/help/matlab/ref/colon.html

Answer 1

[Walter Roberson]

X = A : B : C

is like

X = [];
temp = A;
if B > 0
  while temp <= C
    X = [X, temp];
    temp = temp + B;
  end
elseif B < 0
  while temp >= C
    X = [X, temp];
    temp = temp + B;
  end
end

In the case of 1:2:3, with positive increment, you check whether 3 is less than 1, and since it is not less than your result will have at least one result in it. Start with the 1 in the list. Add the increment, 2, to that value. The result, 3, is not greater than the end point (3), so add the result to the list, so the list is [1 3] now. Add the increment 2 to that last value, getting 5. 5 is greater than the end point of 3, so stop. The list is finished.

Another way of saying this is: the numbers starting at 1, and no more than 3, that are 2 apart from each other. 1 and 3 satisfy that so they are both included.

[Jan]

+1 for the last sentence, which is a rare case of English being leaner and more clear then Matlab.

Answer 2

[YOGESH RAMESH]

B(1:2,3)

[Walter Roberson]

As examined above, 1:2:3 is the list of numbers that includes 1 and 3. You would then index B at locations 1 and 3. Linear indexing would be used, so if B were 2 x 4

b11 b12 b13 b14
b21 b22 b23 b24

then entry #1 and #3 would be b11 and b12

Answer 3

[Mustafa Ahmed]

c = 1:2:5

c = 1×3

1 3 5

[Walter Roberson]

The numbers starting at 1, and 2 apart, and do not exceed 5. So 1, 3, 5