Repeat copies of array elements using for loop/while

2022 2 26
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更新时间：2022 2 27
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0 个投票

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?

6 个评论
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Image Analyst
Image Analyst 2022-2-26
Why? You didn't tag it as homework so since it's not your homework why won't you use repelem()?
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
Image Analyst 2022-2-27
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].
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
Image Analyst 2022-2-27
What if you subtract 1 from i before multiplying it by 2?
Juan Pérez Álvarez
编辑：Image Analyst 2022-2-27
Finally I figured out. Thank you. Got it:
for i =1:4
Vec((2*i)-1:i*2) = i;
end

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 采纳的回答

Image Analyst
Image Analyst 2022-2-27

1 个投票

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

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