Find highest/lowest value in matrix

very basic question: How can I find the highest or lowest value in a random matrix. I know there is a possibility to say开发者_开发问答:

a = find(A>0.5)

but what I'm looking for would be more like this:

A = rand(5,5)
A = 
0.9388    0.9498    0.6059    0.7447    0.2835
0.6338    0.0104    0.5179    0.8738    0.0586
0.9297    0.1678    0.9429    0.9641    0.8210
0.0629    0.7553    0.7412    0.9819    0.1795
0.3069    0.8338    0.7011    0.9186    0.0349

% find highest (or lowest) value

ans = A(19)%for the highest or A(7) %for the lowest value in this case

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Have a look at the min() and max() functions. They can return both the highest/lowest value, and its index:

[B,I]=min(A(:)); %# note I fixed a bug on this line!

returns I=7 and B=A(7)=A(2,2). The expression A(:) tells MATLAB to treat A as a 1D array for now, so even though A is 5x5, it returns the linear index 7.

If you need the 2D coordinates, i.e. the "2,2" in B=A(7)=A(2,2), you can use [I,J] = ind2sub(size(A),I) which returns I=2,J=2, see here.

Update
If you need all the entries' indices which reach the minimum value, you can use find:

I = find(A==min(A(:));

I is now a vector of all of them.

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For matrices you need to run the MIN and MAX functions twice since they operate column-wise, i.e. max(A) returns a vector with each element being the maximum element in the corresponding column of A.

>> A = rand(4)

A =

         0.421761282626275         0.655740699156587         0.678735154857773         0.655477890177557
         0.915735525189067        0.0357116785741896         0.757740130578333         0.171186687811562
         0.792207329559554         0.849129305868777         0.743132468124916         0.706046088019609
         0.959492426392903         0.933993247757551         0.392227019534168        0.0318328463774207

>> max(max(A))

ans =

         0.959492426392903

>> min(min(A))

ans =

        0.0318328463774207

Note that this only works for matrices. Higher dimensional arrays would require running MIN and MAX as many times as there are dimensions which you can get using NDIMS.

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Try this out

A=magic(5)
[x,y]=find(A==max(max(A))) %index maximum of the matrix A 
A_max=A(x,y)
[x1,y1]=find(A==min(max(A))) %index minimum of the matrix A 
A_min=A(x1,y1)