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Can someone explain me how to make this loop efficiently?

조회 수: 1(최근 30일)
Santos García Rosado
Santos García Rosado 2021년 2월 17일
댓글: Santos García Rosado 2021년 2월 18일
Hello Mathworks community!
I'm having a bit of trouble trying to code a for loop. This is my code so far.
randomNumber1 = 100;
randomNumber2 = 150;
out(1)= 0;
B = 4;
for idx = 2:1:numel(A)
if idx <=(B)
ArrayValue = SomeArray(1);
if % first condition
out(idx) = ((out(idx - 1)) - randomNumber1);
elseif % second condition
out(idx) = ((out(idx - 1)) - randomNumber2);
elseif % third condition
out(idx) = (out(idx - 1) + ArrayValue);
end
elseif idx >(B) && idx <= (2*B)
ArrayValue = SomeArray(2);
if % first condition
out(idx) = ((out(idx - 1)) - randomNumber1);
elseif % second condition
out(idx) = ((out(idx - 1)) - randomNumber2);
elseif % third condition
out(idx) = (out(idx - 1) + ArrayValue);
end
elseif idx >(2*B) && idx <= (3*B)
ArrayValue = SomeArray(3);
% It keeps going until I've used every "SomeArray" value
end
end
As you can see, I have to repeat all the statements as many times as values I have inside my vector: SomeArray
The code works as it should, but I'm well awared that this is not how you do it properlly. I know aswell that it is possible to only state the conditions one time, I'm just not sure how to do it.
Could someone help me out?
Thank's!
Santos

채택된 답변

Jon
Jon 2021년 2월 17일
I think the key is coming up with an expression that gives you the index for someArray from the current loop index. Something like this:
randomNumber1 = 100;
randomNumber2 = 150;
out(1)= 0;
B = 4;
for idx = 2:1:numel(A)
k = ceil(idx/4); % index into someArray
ArrayValue = SomeArray(k);
if % first condition
out(idx) = ((out(idx - 1)) - randomNumber1);
elseif % second condition
out(idx) = ((out(idx - 1)) - randomNumber2);
elseif % third condition
out(idx) = (out(idx - 1) + ArrayValue);
end
end
  댓글 수: 2
Santos García Rosado
Santos García Rosado 2021년 2월 18일
Thank you Jon! Your code was what i was looking for. Indeed, I had preallocated the array but I forgot to cipying it down on the answer. Thank's again.

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추가 답변(1개)

Rik
Rik 2021년 2월 17일
편집: Rik 2021년 2월 17일
Your intuition is correct; this can indeed be simplified:
for k=1:numel(SomeArray)
if idx <= (k*B)
ArrayValue = SomeArray(k);
%your other code
break%stop the for loop with k
end
end
  댓글 수: 1
Santos García Rosado
Santos García Rosado 2021년 2월 18일
Thank's Rik! Exactly what I was looking for.

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