Is there a function for argmax?

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Javier Biera
Javier Biera 2018-7-5
评论： Walter Roberson 2020-1-7
I am looking for a function that selects the argmax value from a vector.
aux = argmax(P); %P is a normal vector
Supposedly there should a function directly called argmax, but is not working (error = Undefined function or variable 'argmax'). Is there any other function? (I am working with the 2017a version).
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Anton Semechko
Anton Semechko 2018-7-5
编辑：Anton Semechko 2018-7-5
Use syntax
[P_max,id_max]=max(P);
Here, id_max is the index of P_max in P, so that P_max == P(id_max)
Stephen23
Stephen23 2018-7-5
编辑：Stephen23 2018-7-5
@Javier Biera: did you read the max documentation? It's second output is an index:
[~,idx] = max(...)

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回答（2 个）

Image Analyst
Image Analyst 2018-7-5
It's probably some function that someone wrote, like the person who gave you the code. Ask them for it. Otherwise, can you tell us how aux is used? That may give us some clue as to what argmax gives. Like it really should be nargin (the number of input arguments) or the max value of some matrix inputted into the argument list or who knows what.
Alan
Alan 2020-1-6
function y = argmax(x)
[~,y] = max(x);
end
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Alan
Alan 2020-1-7
That is a step more comprehensive, but to cover all the edge cases would need a lot more work. In my opinion, there should be a standard MATLAB function for this.
Walter Roberson
Walter Roberson 2020-1-7
Easier I suspect to return
y == max(x, [], dim);
which would be a logical the same size as the original. That removes the need to worry about different sizes of output for different columns.

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