Check for identical maximum values in an array

Asked by Jane Ak on 6 Sep 2017

Latest activity Answered by Jane Ak on 6 Sep 2017

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Hi guys, I have a matrix, A = [2 4 1;8 3 2;8 8 6;4 5 3] As seen, the above matrix has more than one maximum values. How do i write an if statement testing for multiple maximum values? That is: if (code) % if more than one maximum value exists; ...; % do ... end

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4 Answers

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Answer by Walter Roberson on 6 Sep 2017

Accepted Answer

"if more than one maximum value exists in the array pick the first max value and display it's index"

idx = find( A(:) == max(A(:)) );
if length(idx) > 1
  disp(idx(1))
end

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Answer by Star Strider on 6 Sep 2017

Probably the easiest way is to do logical indexing and count the number of non-zero elements to get the number of maximum values:

A = [2 4 1;8 3 2;8 8 6;4 5 3];
nr_maxvals = nnz(A == max(A(:)));
nr_maxvals =
     3

3 Comments

Jane Ak on 6 Sep 2017

thank you Star. I'm new to matlab, how can i apply this result to the "if statement"?

Walter Roberson on 6 Sep 2017

if nnz(A == max(A(:))) > 1
   ...
end

Star Strider on 6 Sep 2017

@Walter — Thank you.

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Answer by José-Luis on 6 Sep 2017

Edited by José-Luis on 6 Sep 2017

Number of maximum values:

 numMax=sum(A(:) == max(A(:)));
 if numMax > 1
    %Do your thing
 end

2 Comments

Jane Ak on 6 Sep 2017

Thank you Jose. Pardon my asking, why is the sum there? Also my if statement is stated thus:

if %more than one maximum value exists in the array
%pick the first max value and display it's index
end

I'm thinking of how to apply this to your answer above. Thank you again for your time

Stephen Cobeldick on 6 Sep 2017

@Jane Ak: Star Strider already explained that in their answer from three hours ago.

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Answer by Jane Ak on 6 Sep 2017

Thanks alot guys. I thought I could accept more than 1 answer. you guys are the real MVPs.

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