Extract columns into new variables efficently

Hi Mathwork's community,

So I have a Matrix A such as:

A= [1 1 2 2 3 3 1 1 2 2 3 3; 1 1 2 2 3 3 1 1 2 2 3 3];

And a matrix B, which is the matrix that I'd like to separate into three different variables. (Note: There will always be three variables).

B = [10 20 30 40 50 60 70 80 90 100 110 120; 1 2 3 4 5 6 7 8 9 10 11 12];

Variable1 corresponds to B positions where A values are equal to 1, Variable2 corresponds to B positions where A values are equal to 2 and Variable3 corresponds to B positions where A values are equal to 3. The expected output should be:

Variable1 =[10 20 70 80; 1 2 7 8]
Variable2 = [30 40 90 100 ; 3 4 9 10]
Variable3 = [50 60 110 120; 5 6 11 12]

Could somone please help me out?

Santos

[Walter Roberson]

What do you want to have happen for the case where the first row of A has a different value than the corresponding position in the second row of A?

Will the three unique values in A always be 1, 2, and 3, or could it be (for example) 7, 29, 31 ? Negatives? Fractions?

[Santos García Rosado]

Hello Walter. Thank's for the question. Clearly, I didn't make my-self clear enoguh on that part. All the rows of A will be equal to the first row and will always be 1, 2 and 3 values.

Answer 1

[Jeff Miller]

A= [1 1 2 2 3 3 1 1 2 2 3 3; 1 1 2 2 3 3 1 1 2 2 3 3];
B = [10 20 30 40 50 60 70 80 90 100 110 120; 1 2 3 4 5 6 7 8 9 10 11 12];
type1 = A(1,:) == 1;
Variable1 = B(:,type1);
% et cetera

[Santos García Rosado]

Thank's Jeff. That'll do.