CODEWITHSUNDEEP
matlabmatrixindexingsetdimension
Eka Kurniawan
Eka Kurniawan

Reputation: 13

Matlab: Setting Value Based on Index and Dimension

I have a matrix as follow.

octave:63> a
a =

ans(:,:,1) =

   0.411710   0.947670
   0.068291   0.368340

ans(:,:,2) =

   0.27178   0.56699
   0.54317   0.27393

ans(:,:,3) =

   0.72621   0.44131
   0.22743   0.61914

Using max function, I can get the index of maximum value based on certain dimension.

octave:64> [a2_val a2_indx] = max(a, [], 2)

a2_indx =

ans(:,:,1) =

   2
   2

ans(:,:,2) =

   2
   1

ans(:,:,3) =

   1
   2

If I have the same matrix as a with zero values, is there any way I can mark the maximum location with 1? Something like follow.

octave:65> z
z =

ans(:,:,1) =

   0   1
   0   1

ans(:,:,2) =

   0   1
   1   0

ans(:,:,3) =

   1   0
   0   1

I prefer the solution to be dimension-free like the max function capable of.

Thanks.

Upvotes: 1

Views: 525

Answers (1)

trutheality
trutheality

Reputation: 23455

Simplest way is probably to replicate the max matrix along that dimension and use logical comparison:

dim = 2; % The dimension along which we max

% Prep a size matrix for the replication
dims = ones( size( size( a ) ) );
dims( dim ) = size( a, dim ); % (all ones except the
                              % dimension that gets maxed)

result = ( a == repmat( max( a, [], dim ), dims ) )

Upvotes: 1

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