I have to switch the max and min elements in a vector and assume vec = ceil(rand(1, 10)*100) is a vector containing 10 random generated integers. The script i have to provide will swap the maximum and the minimum element in the vector.

I don't even know where to start, any help? Example: vec=[ 16 98 96 49 81 15 43 92 80 96], you script will result in vec = [ 16 15 96 49 81 98 43 92 80 96]

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

Answer 1

[ANKUR KUMAR]

Firstly, please follow Walter Roberson's comment.

   A=[ 16 98 96 49 81 15 43 92 80 96]
  A([find(A==min(A)),find(A==max(A))])=ones(1,length(find(A==min(A))))*max(A),ones(1,length(find(A==max(A))))*min(A)]

[Bruno Luong]

This answer won't work if there is tie in min or max

[ANKUR KUMAR]

If there is a tie in min and max, then all elements of matrix must be same.

[Bruno Luong]

Sorry for confused statement, "tie" means there is more than one element of the array reach the min-value (not minvalue==maxvalue), eg

a = [1, 3, 2, 1, 10]

Same issue with max. The array is not constant and your code just crashes

[ANKUR KUMAR]

Oh sorry. I forgot to take this into consideration. This will work.

A = [1, 3, 2, 1, 10]

A([find(A==min(A)),find(A==max(A))])=[ones(1,length(find(A==min(A))))*max(A),ones(1,length(find(A==max(A))))*min(A)]

[ANKUR KUMAR]

I edited my first answer.

Answer 2

[Bruno Luong]

Solution for the problem of "swapping" ties min-values with ties max-values

minA = min(A);
maxA = max(A);
ismax = A==maxA;
A(A==minA) = maxA;
A(ismax) = minA;

[Stephen23]

+1 probably the neatest way to do this.

Answer 3

[Stephen23]

Even though this is homework without any attempt... here is a neat and efficient MATLAB way to do that (this swaps the first minimum and the first maximum):

>> vec = [16,98,96,49,81,15,43,92,80,96]
vec =
   16   98   96   49   81   15   43   92   80   96
>> [~,idn] = min(vec);
>> [~,idx] = max(vec);
>> vec([idn,idx]) = vec([idx,idn])
vec =
   16   15   96   49   81   98   43   92   80   96

Of course you cannot hand this in as your own work, because that would be plagiarism.

[ANKUR KUMAR]

Ops.. Why can not I able to write this at the very attempt? Still at learning stage.

You are worth MVP.

[Bruno Luong]

But your (Ankur's) code and Stephen's code do not perform the same arrangement in the case of tie. And poster never specify which one he actually needs.

[Stephen23]

Swap all tied maximum/minimum values:

>> vec = [15,16,96,96,49,81,15,43,92,80,96]
vec =
   15   16   96   96   49   81   15   43   92   80   96
>> idn = find(min(vec)==vec);
>> idx = find(max(vec)==vec);
>> vec([idn,idx]) = vec([idx(1)*ones(1,numel(idn)),idn(1)*ones(1,numel(idx))])
vec =
   96   16   15   15   49   81   96   43   92   80   15