split a matrix according to a column with matlab.

Question

A = [1,4,2,5,10
     2,4,5,6,2
     2,1,5,6,10
     2,3,5,4,2]

And I want split it into two matrix by the last column A ->B and C

B         


        

Answer 1

Use logical indexing

B=A(A(:,end)==10,:);
C=A(A(:,end)==2,:);

returns

>> B
B =
     1     4     2     5    10
     2     1     5     6    10

>> C
C =
     2     4     5     6     2
     2     3     5     4     2

EDIT: In reply to Dan's comment here is the extension for general case

e = unique(A(:,end));
B = cell(size(e));
for k = 1:numel(e)
    B{k} = A(A(:,end)==e(k),:);
end

or more compact way

B=arrayfun(@(x) A(A(:,end)==x,:), unique(A(:,end)), 'UniformOutput', false);

so for

A =
     1     4     2     5    10
     2     4     5     6     2
     2     1     5     6    10
     2     3     5     4     2
     0     3     1     4     9
     1     3     4     5     1
     1     0     4     5     9
     1     2     4     3     1

you get the matrices in elements of cell array B

>> B{1}
ans =
     1     3     4     5     1
     1     2     4     3     1

>> B{2}
ans =
     2     4     5     6     2
     2     3     5     4     2

>> B{3}
ans =
     0     3     1     4     9
     1     0     4     5     9

>> B{4}
ans =
     1     4     2     5    10
     2     1     5     6    10