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arraysmatlabmax
user4403586
user4403586

Reputation: 23

Max within groups in Matlab

I have the following matrix:

[ 2 5 7 8  1 3 4 6  5 7 3 1;
  1 1 1 1  2 2 2 2  3 3 3 3;]

The first row represents values and the second characteristic

I want to get the max value if the value in the second row is the same, i.e. their characteristic is the same. So, what I would like to have is:

[ 8 6 7], since 8 is the highest value when the second row is 1, 6 when the second row is is 2, and 7 when the second row is 3. I can do it with a loop, but I would like vectorized solution, and if possible of course, in one line.

Upvotes: 1

Views: 49

Answers (1)

Daniel
Daniel

Reputation: 36710

accumarray does exactly what you want

x=[ 2 5 7 8 1 3 4 6 5 7 3 1; 1 1 1 1 2 2 2 2 3 3 3 3;]
accumarray(x(2,:)',x(1,:)',[],@max)

Upvotes: 3

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