Finding value in Matrix to corresponding minvalue Position in different Matrix

Dear all,

I am quite new to Matlab and have the following problem:

I do have 2 Matrices A and B with the same size.

I would like to loop over each row of Matrix A to find the Minimum-value and its Column-Position.

Each resulting Column-position should be taken and looped over Matrix B to find the corresponding column-value.

Afterwards, I should receive a matrix in which I will find the values in following order:

minvalue Matrix A row1

corresponding value at position of minvalue row1 of Matrix A

minvalue Matrix A row2

corresponding value at position of minvalue row2 of Matrix A

and so on....

Afterwards, I would like to normalize the resulting Matrix to ensure, I have all values in a range in between -1 and 1

Can anybody please help me out with this?

I thought about this piece of code, but I do not manage to loop over the second Matrix with the minidx1-values to receive the value of the defined value from Matrix A in Matrix B.

for k1=1:size(A,1)
    [minval1,minidx1] = min(A(k1,:));
    [minval2] = B(:,minidx1:minidx1);
    Result{k1}=[minval1,minval2]
end

A=cell2mat(Result)
A=transpose(A)
A=normalize(A)

P.S.: sub2ind is not working, I use R2021b. :(

Many thanks in advance to all those Matlab-cracks out there :)

[Bruno Luong]

"I am quite new to Matlab"

You posted a MATLAB question in 2017. How come you are still new to MATLAB six year later?

[Alexander Hummel]

Hi Bruno,

One more question:

Do you know any possibility to do the same code, but instead of taking one min-value, of Matrix A I would like to take two values (max-peaks each row) and find the corresponding values in Matrix B each row.

I thought about findpeaks, but this is not proper working- I think it is dedicated to work only with one value.

many thanks!!

[Bruno Luong]

Checkout the mink command

Answer 1

[Bruno Luong]

A=randi(10,5)

A = 5×5

4 6 5 1 10 3 7 3 5 10 4 1 9 3 3 10 5 2 10 1 2 5 7 7 2

B=randi(10,5)

B = 5×5

7 1 9 6 5 7 7 8 2 7 4 9 5 10 10 3 10 2 6 7 5 6 1 1 5

[Amin,jmin]=min(A,[],2)

Amin = 5×1

1 3 1 1 2

jmin = 5×1

4 1 2 5 1

% Amin  is A(sub2ind(size(A),(1:size(A,1))',jmin))
% Bmin = B(sub2ind(size(B),(1:size(B,1))',jmin))
m  = size(B,1);
Bmin = B((1:m)'+ m*(jmin-1)) % EDIT

Bmin = 5×1

6 7 9 7 5

[Amin,Bmin]

ans = 5×2

1 6 3 7 1 9 1 7 2 5

[Alexander Hummel]

Many thanks! :)

Unfortunately, I can not use sub2ind because I am using R2021b.

Do you know any alternative way??

:)

[Dyuman Joshi]

sub2ind was introduced before R2006a. That's not a reason to not use it.

"P.S.: sub2ind is not working, I use R2021b. :("

What exactly "not working" means in this context?

[Bruno Luong]

sub2ind is as old as the earth. You either corrupt or shadow the stock function sub2ind. Otherwise replace with

m  = size(B,1);
Bmin = B((1:m)'+ m*(jmin-1))

[Alexander Hummel]

Hi Bruno,

many thanks. I just read in the documentation that sub2ind is supported after 2021b.

But I was mistaken. I think I mixed it up.

As you mentioned:

Introduced before R2006a

Your code works fine.

MANY THANKS