How can I sort a matrix to match another matrix?

Hello everybody,

I have a question regarding the sorting. I have 2 matrices, A and B. For example:

A = [11 1; 12 1; 13 1; 21 2; 23 2; 31 3; 33 3; 41 4]

B = [1; 2; 1; 3; 1; 4; 2; 3]

How can I sort A (randomly each time) that the 2 column of A is same with B? Such as:

A = [12 1; 23 2; 11 1; 31 3; 13 1; 41 4; 21 2; 33 3]

Stay happy and healty..

Answer 1

[Stephen23]

>> [~,idx] = sort(B);
>> [~,idx(idx)] = sort(A(:,2));
>> A = A(idx,:)
A =
   11    1
   21    2
   12    1
   31    3
   13    1
   41    4
   23    2
   33    3

[Doli Swey]

Thank you very much Stephan. This do what I want. However, it always sort in acending order. Is there any way to make this random?

[Stephen23]

"Is there any way to make this random"

Ah, I missed that part of the question. Give me a few minutes.

EDIT: probably a simple loop is the best approach:

A = [11,1;12,1;13,1;21,2;23,2;31,3;33,3;41,4]
B = [1;2;1;3;1;4;2;3]
C = B(:,[1,1]);
for k = 1:max(B)
    X = find(B==k);
    X = X(randperm(numel(X)));
    C(X,:) = A(A(:,2)==k,:);
end

Giving:

>> C
C =
   12    1
   23    2
   11    1
   31    3
   13    1
   41    4
   21    2
   33    3

[Doli Swey]

Yes!. Thank you very much Stephan. All best..

[Doli Swey]

Hello again Stephan, I have a problem regarding to

A (:, 2) == k

Since my A is a string array and k is double, I cannot proceed.

I have attached the A variable (CombinedStim).

I tried to use str2double and got NAN values ​​because the first column contains strings, whereas second column is numbers.

Then i try regexp, however I was not succesfull again.

Do you have any idea that I can make this work?

[Stephen23]

"Do you have any idea that I can make this work?"

Possibly you could replace the RHS with a string (or character vector) of the number:

A(:,2) == num2str(k)

"...the first column contains strings, whereas second column is numbers."

I strongly recommend that you convert the data into a table, then the first column would be strings and the second column really would be numbers (not strings encoding numbers). Numeric data should be efficiently stored as numeric, which also makes processing it much easier.

[Doli Swey]

I understand! Thank you so much. Have a wonderful day