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how can i make a function which will return the largest and the second largest component?

Asked by felix on 18 Nov 2012

how can i make a function that accepts as input a vector of integers, which will return the largest and the second largest component of the vector for the first i think that is max1=max(max(C)) any idea for max2?

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felix

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2 Answers

Answer by Jan Simon on 18 Nov 2012
Edited by Jan Simon on 19 Nov 2012
Accepted answer

Do you mean the maximum over a matrix (see tags and example max(max(C))) or over vector (body of the question)?

  1. Find maximum value with the corresponding index
  2. Set value of this index to NaN
  3. Find maximum again.

Alternative, which is slower due to the expensive sorting for large inputs:

  • SORT helps.

Which values should be replied, if the highest maximum is not unique?

[EDITED: Sorry, I've overseen that this is a homework!]

2 Comments

felix on 18 Nov 2012

over vector. i have a vector with random number and i have to find the max and the second max number of the vector without using unique or short...

Jan Simon on 19 Nov 2012

I think: "short" means "sort".

Sorry, felix, that I've solved your homework. Now it gets hard to submit it without cheating. Remember, that your teacher/assistent knwos this forum also, so it is strongly recommended to mention all sources.

Jan Simon
Answer by Jurgen on 18 Nov 2012
Edited by Jurgen on 18 Nov 2012

Or:

 if sum(C==max(C))==1 
     second = max(C(C<max(C)));
 else
     second = max(C);
 end

i.e. test if the maximum is unique, if the max is not unique the second is equal to max(C)

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Jurgen

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