MATLAB: New matrix from all based on some criteria

keep observationsmake smaller matrix

Hi,

Probably this is a very simple question, but I am new to Matlab and can't find the answer so would appriciate your help.

For example, I have a matrix: A= [1, 2, 4; 2 , 3, 1; 2, 3, 5; 1 , 2, 1];

How can I create another matrix based on criteria that, for example, value in second column is 2? What I want to get is:

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

Thanks!

Best Answer

B = A(A(:,2) == 2,:)

Related Solutions

MATLAB: Find Minimum based on new criteria

This works:

row = (A(:,3) == min(A(A(:,5)==1,3))) & (A(:,5) == 1);  % Row Index (Logical Vector)
Result = A(row,:)                                       % Desired Row

If you want the number index of the row, use the find function:

row_index = find(row);

MATLAB: Extracting a matrix by row and column from a large matrix

I changed your example matrix a bit to make sure it ignores partial pattern matches.

m = [1 1 1    2000
    1 1 1    2000
    1 1 1    2000
    2 2 2    3000
    2 2 2    3000
    2 2 2    3000
    3 3 3    5000
    3 3 3    5000
    3 3 3    5000
    2 2 2    6000
    2 2 2    6000
    9 9 9    7000];
s = [2 2 2
    2 2 2
    2 2 2];
[~, rowIdx] = intersect(m,s); 
mSubset = m(rowIdx+(0:size(s,1)-1),:);

Result

mSubset =
           2           2           2        3000
           2           2           2        3000
           2           2           2        3000

Note that if there is more than 1 match it will only return the first subset match.

Best Answer

Related Solutions

MATLAB: Find Minimum based on new criteria

MATLAB: Extracting a matrix by row and column from a large matrix

Related Question