How can i divide a (matrix) into two parts

i have a 300*10 matrix. i want to divide it into two parts. the size of desired parts are 240*10 and 60*10 respectively.

A=[]10*300 % is given
B=[]10*240 % i can generate it
C=[]10*60 % i need help in this part, columns of matrix A which are not in matrix B should produce matrix C

would you give me an advice?thank you very much

[James Tursa]

What is the code you used to generate B? Can you modify that code to generate C also?

[maryam]

this is how i generate B:

idx=randsample(300,240);
idx=idx';
for i=1:240;
     B(:,i)=A(:,idx(i));
end

i want rest of matrix A columns produce matrix C

[dpb]

This doesn't do what you say you want...you say you want B and C with 10 columns; you've loaded B as 240x240 as the above is written.

Clarify what you really do mean, precisely.

Answer 1

[Andrei Bobrov]

idx=randsample(300,240);

or

idx = randperm(300,240);

B = A(idx,:);

C = A(~ismember((1:size(A,1))',idx),:); %

or

C = A(setdiff((1:size(A,1))',idx),:);

or

C = A(setxor(1:size(A,1),idx),:);

[maryam]

thank you for your help, it works :)

Answer 2

[dpb]

Hard as James says to envision how you could do B and not be able to figure out C but

C=A(241:end,:);

Mayhaps it's end you were struggling with altho the workaround w/o the "syntactic sugar" of the builtin function isn't hard...

C=A(241:size(A,1),:);

or use an intermediary variable.

[nRow,nCol]=size(A);

ADDENDUM

OK, so you want a random permutation of the rows...

...scratch previous, it solves the problem I thought was asked for but the asking is conflicting in dimensions with the proposed example partial solution...

[maryam]

please notice to my above reply. do you have any suggestion?