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creating loop with two variables

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sermet
sermet on 7 Dec 2017
Answered: Jan on 7 Dec 2017
For example;
a=0:2:10;
b=0:2:6;
% number of elements of a is always bigger than b
I need to create for loop as below;
result(1)=a(1)-b(1);
result(2)=a(2)-b(2);
result(3)=a(3)-b(3);
result(4)=a(4)-b(4);
result(5)=a(5)-b(4);
result(6)=a(6)-b(4);
Since a and b variables' number isn't constant for each problem. How can I create this loop for working properly with arbitrary numbers of a and b?

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Accepted Answer

Birdman
Birdman on 7 Dec 2017
Edited: Birdman on 7 Dec 2017
for i=1:max(numel(a),numel(b))
if(i>=min(numel(a),numel(b)))
result(i)=a(i)-b(min(numel(a),numel(b)));
else
result(i)=a(i)-b(i);
end
end

  3 Comments

Stephen Cobeldick
Stephen Cobeldick on 7 Dec 2017
Seven lines of code... see my answer for a simpler solution.
Birdman
Birdman on 7 Dec 2017
Your answer is of course simpler but he mentioned to do it with a for loop, therefore I wrote this. Otherwise of course I would have written something like you did.
KL
KL on 7 Dec 2017
You could call numel, outside the loop and store its output in a variable (after finding min and max) and only use this variable inside the loop.
Now, you're calling min and numel so many times (sometimes even twice within the same iteration).

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More Answers (2)

Stephen Cobeldick
Stephen Cobeldick on 7 Dec 2017
Edited: Stephen Cobeldick on 7 Dec 2017
Why waste time writing an ugly loop? Here is a simpler solution in just two lines:
>> a = 0:2:10;
>> b = 0:2:6;
>> v = 1:max(numel(a),numel(b));
>> a(min(v,end))-b(min(end,v))
ans =
0 0 0 0 2 4

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Jan
Jan on 7 Dec 2017
% number of elements of a is always bigger than b
This was not considered in the other suggestions. Another solution:
a = 0:2:10;
b = 0:2:6;
result = a - b(min(1:numel(a), numel(b)))

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