Finding the Index number that corresponds to a specific value

Can any one help me how can i determine the index number that coresponds to a value in a matrix? for example, I've this : >> [val2 index2] = max(max(C_IA))

val2(:,:,1) =

31.3781 + 0.0000i

val2(:,:,2) =

30.0139 - 0.0000i

val2(:,:,3) =

27.7915 + 0.0000i

index2(:,:,1) =

     1

index2(:,:,2) =

     1

index2(:,:,3) =

     3
how can i find index2 value which corresponds to the maximum of val2?
in our case here, the solution is to get index2 = 1 as it corresponds to maximum of val2 = 31.3781 but how can i do it in matlab?
I was trying to write something like find(index2 == max(val2)) but it doesn't work.

[Hisham]

Dear all, thanks alot for your responses however this is not what I want. May be I was not so clear in my question so let me explain it agian. What I want is not to find the index of max(C_IA), I will paste below my Input and then state what I want to get: I've originally the following matrix: >> C_IA

C_IA(:,:,1) =

31.3781 + 0.0000i  26.0762 - 0.0000i  29.2083 - 0.0000i
30.1921 - 0.0000i  27.8010 + 0.0000i  26.0254 - 0.0000i
27.9994 - 0.0000i  26.7921 - 0.0000i  27.7583 + 0.0000i

C_IA(:,:,2) =

29.1817 + 0.0000i  28.4916 + 0.0000i  28.6310 + 0.0000i
30.0139 - 0.0000i  29.9155 + 0.0000i  27.0452 - 0.0000i
28.4040 + 0.0000i  27.7000 + 0.0000i  28.3678 + 0.0000i

C_IA(:,:,3) =

26.7694 - 0.0000i  24.7692 - 0.0000i  27.7915 + 0.0000i
26.8899 - 0.0000i  26.0439 - 0.0000i  24.7235 - 0.0000i
26.9859 + 0.0000i  24.8153 + 0.0000i  26.2597 - 0.0000i

Please note that the above output was my result I wanted of a three nested for loops (for K1=1:3 then for K2=1:3 then for K3=1:3)

then I calculated the index of the max of C_IA on three steps in order to know which K1,K2 and K3 values has achived the max(C_IA(:))

[val1 index1] = max(C_IA) [val2 index2] = max(max(C_IA)) [val3 index3] = max(max(max(C_IA)))

when I run the above, I get the following for the first line: >> [val1 index1] = max(C_IA)

val1(:,:,1) =

31.3781 + 0.0000i  27.8010 + 0.0000i  29.2083 - 0.0000i

val1(:,:,2) =

30.0139 - 0.0000i  29.9155 + 0.0000i  28.6310 + 0.0000i

val1(:,:,3) =

26.9859 + 0.0000i  26.0439 - 0.0000i  27.7915 + 0.0000i

index1(:,:,1) =

     1     2     1

index1(:,:,2) =

     2     2     1

index1(:,:,3) =

     3     2     1

and as we have max(C_IA(:)) = 31.3781 then I want to get the first element value of index1 that corresponds to 31.3781 (in this case index1=1

Same for the 2nd step: >> [val2 index2] = max(max(C_IA))

val2(:,:,1) =

31.3781 + 0.0000i

val2(:,:,2) =

30.0139 - 0.0000i

val2(:,:,3) =

27.7915 + 0.0000i

index2(:,:,1) =

     1

index2(:,:,2) =

     1

index2(:,:,3) =

     3

I wanted to get index2 value that corresponds to 31.3781 value (in this case index2=1)

for the last step [val3 index3] = max(max(max(C_IA))) it's clear since what i want is exactly index3 output.

My question is: how can i get index2 value that corresponds to 31.3781 in this case?

[Sean de Wolski]

See edit

Answer 1

[Sean de Wolski]

EDIT

If you want the dimensional indices of the maximum value in the matrix, use max and ind2sub

x = rand(3,3,3);
[mxv,idx] = max(x(:));
[row,col,pag] = ind2sub(size(x),idx)

And for more info, as Bjorn has pointed out:

doc ind2sub

[Sean de Wolski]

See Edit

[Hisham]

thanks alot Sean de Wolski , your simple two lines has solved my problem .. amazing, thanks sooooooooo much :) :)

Answer 2

[Bruno Pop-Stefanov]

You can use the find function on your input matrix directly. If I am correct, C_IA should be 3-dimensional. In your case, you would write:

maxval = max(max(max(C_IA)));
index = find(C_IA == maxval);

'index' is the linear index of the max of C_IA. You can then access the element by writing

C_IA(index)

or you can transform this linear index into subscripts using ind2sub.