Find values in 2D array corresponding to vector of indices obtained from another array

Hello!

I have a 3 x (variable number, in this case 5) array amp:

amp =
Columns 1 through 5
0.04                      0.05                      0.06                      0.07                      0.05
0.07                      0.03                      0.02                      0.06                      0.06
0.06                      0.03                      0.06                      0.04                      0.07

Indices idx of the maximum value for each column are as follows:

idx =
2     1     1     1     3

I have another 3 x 5 array frq

frq =
50    16    18    50    50
50    25    25    50    43
47    20    20    50    39

and would like to get a vector of the values in frq that correspond to the indices for the row shown in idx. That should be

50 16 18 50 39

frq(idx) or frq(:,idx) come up with a mess, and I have tried to use sub2ind and also come up with a mess. I'm sure this could be done in a loop easily, but would like to know how to do it the "MATLAB" way!

Thanks.

Doug Anderson

Answer 1

[Voss]

amp = [0.04 0.05 0.06 0.07 0.05
       0.07 0.03 0.02 0.06 0.06
       0.06 0.03 0.06 0.04 0.07];
frq = [50 16 18 50 50
       50 25 25 50 43
       47 20 20 50 39];
[~,idx] = max(amp,[],1);

[m,n] = size(frq);
result = frq(sub2ind([m n],idx,1:n))

result = 1×5

50 16 18 50 39

[Douglas Anderson]

Thank you! That clears up my sub2ind mistakes.

[Voss]

You're welcome!