Repeat copies of array elements using for loop/while

Hi, I need create a code where the elements of an array are repeat:

For example:

% Create a simple vector:
for i =1:4
    Vec(i) = i;
end
Vec = [1,2,3,4];

If I need repeat the elements of this vector 2 times:

Vec = [1,1,2,2,3,3,4,4];

3 times:

Vec = [1,1,1,2,2,2,3,3,3,4,4,4];

I know using the function: repelem; I can get this result but I need do it using a for loop/while.

¿Any idea?

[Image Analyst]

Why? You didn't tag it as homework so since it's not your homework why won't you use repelem()?

[Juan Pérez Álvarez]

The logic my friend, its too easy use the matlab functions, I want create my owns functions. For example, I create my own functions to find max and min values from arrays (and I know the max and min function exist). I need understand the logic, because with that logic I can repeat a code in others lenguajes. (by the way, sorry for my english).

Note: It's not homework.

[Image Analyst]

OK, if you want to create your own, then I'll let you do it. I'll just give a hint if you want it. The index "i" in the loop should be a vector of length 2 that specifies a starting and stopping index, like instead of 2 it should be [3:4].

[Juan Pérez Álvarez]

Got it, but i don't understand where I defind the index. I try this:

for i = 1:3

Vec([i+1:i+2]) = i;

end

And I know I need to find an index that in iteration 1 is like:

[1:2]

and the second iteration is:

[3:4]

But i don´t have idea. Another clue?

[Image Analyst]

What if you subtract 1 from i before multiplying it by 2?

[Juan Pérez Álvarez]

Finally I figured out. Thank you. Got it:

for i =1:4
    Vec((2*i)-1:i*2) = i;
end

Answer 1

[Image Analyst]

I'd do it slightly differently:

Vec = 1 : 4;
n = 3; % Number of times to repeat each element of Vec
Vec2 = zeros(1, 2 *  length(Vec));
for k = 1 : length(Vec)
    index1 = (k-1) * n + 1;
    index2 = index1 + n - 1;
    Vec2(index1 : index2) = Vec(k);
end
Vec2