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How to calculate a max value in a array without the built in functions.

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Giuseppe
Giuseppe on 12 Mar 2014
Answered: Shivani Dixit on 1 Jun 2021
The array is
Time = [1,6,3,6,8,12,1]
I think you need to use a for or while loop. There is no predetermined max value however as it is time.
Thanks.

Accepted Answer

Mischa Kim
Mischa Kim on 12 Mar 2014
Edited: Mischa Kim on 12 Mar 2014
Giuseppe, a for-loop would be the way to go:
maxval = Time(1);
for ii = 1:length(Time)
if Time(ii) > maxval
maxval = Time(ii);
end
end
Alternatively, you could use max(Time).
  3 Comments
Steven Lord
Steven Lord on 21 Apr 2020
Of course it does. But the terms of the homework assignment (which Mischa's solution technically violates, as > is a built-in function) prohibit the use of built-in functions. This information is in the title of the original question, not the body. [Yes, technically the question doesn't state this was a homework assignment, but I've been on Answers and the MATLAB newsgroup before that for long enough to know a homework question when I read it.] Two such functions:
Time = [1,6,3,6,8,12,1];
[maxValue, maxLocation] = max(Time)
[maxValue2, maxLocation2] = maxk(Time, 1)
If you're willing to allow a bit more work:
[sortedTime, sortedIndices] = sort(Time, 'descend');
maxValue3 = sortedTime(1)
maxLocation3 = sortedIndices(1)
If Time were an array rather than a vector and you're using release R2018b or later of MATLAB, you can use max. Though if you want the linear index second output, you need to use release R2019a or later.
TimeA = reshape(randperm(4*5*6), [4 5 6]);
maxValue4a = max(TimeA, [], 'all')
[maxValue4b, maxLocation4b] = max(TimeA, [], 'all', 'linear')
I suspect the goal of the assignment was for the students to practice using loops to walk through the elements of an array, processing each element in turn as Mischa's solution does.

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More Answers (2)

Carlos
Carlos on 12 Mar 2014
Edited: Carlos on 12 Mar 2014
A very easy newbie way to do it using a while loop (better with a for loop as Mischa states)
>> Time = [1,6,3,6,8,12,1];
>> max=Time(1);k=1;
>> while(k<=length(Time))
if(Time(k)>max)
max=Time(k);
end
k=k+1;
end
  3 Comments
Giuseppe
Giuseppe on 14 Mar 2014
thank you this is still useful. now i understand more about while vs for loops.

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Shivani Dixit
Shivani Dixit on 1 Jun 2021
You can use for loop or while loop for finding out the maximum or minimum element in the array without using any built-in functions.
Finding out maximum value in an array using for loop is shown below:
Time = [1,6,3,6,8,12,1];
ans = Time(1); % Initially take maximum element as first element and after iterating over the loop we will get final answer
for i=1:length(Time)
if(Time(i)>ans)
ans=Time(i);
end
end
% The variable 'ans' would store the final maximum value

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