Randomly deleting a 'one' in a column of a binary matrix
1 view (last 30 days)
Show older comments
Hi,
I have a matrix that looks like this:
1 1 1 1 1 1
0 1 1 1 1 1
0 0 1 1 1 1
0 0 1 1 1 1
0 0 0 1 1 1
0 0 0 1 1 1
0 0 0 0 1 1
0 0 0 0 1 1
0 0 0 0 0 1
0 0 0 0 0 1
What should I do when I randomly want to delete a 'one' in (let's say) column 4? Thanks in advance,
Tim
0 Comments
Accepted Answer
Wayne King
on 11 Oct 2012
Edited: Wayne King
on 11 Oct 2012
If you want to just choose one of the 1's from the matrix to set equal to 0, then
indices = find(A>0);
chooseset = randperm(length(indices));
index = chooseset(1);
A(indices(index)) = 0;
If you really want to restrict it to just column 4
indices = find(A(:,4)>0);
chooseset = randperm(length(indices));
index = indices(chooseset(1));
A(index,4) = 0;
Recently randperm() has been updated so you can just get 1 value back.
indices = find(A(:,4)>0);
choice = randperm(length(indices),1);
index = indices(choice);
A(index,4) = 0;
More Answers (1)
Azzi Abdelmalek
on 11 Oct 2012
Edited: Azzi Abdelmalek
on 11 Oct 2012
A=[1 1 1 1 1 1
0 1 1 1 1 1
0 0 1 1 1 1
0 0 1 1 1 1
0 0 0 1 1 1
0 0 0 1 1 1
0 0 0 0 1 1
0 0 0 0 1 1
0 0 0 0 0 1
0 0 0 0 0 1]
m=size(A,2)
idx=randi(m,1)
A(:,idx)=[] % this will remove column number idx
%I 'm not sur what you mean by delete a one, if you want raplace them by 0
A(:,idx)=0
4 Comments
Azzi Abdelmalek
on 11 Oct 2012
Edited: Azzi Abdelmalek
on 11 Oct 2012
Tim you did'nt read all the answer, at the end I said use
A(:,idx)=0
istead of
A(:,idx)=[]
which means use the below code
m=size(A,2)
idx=randi(m,1)
A(:,idx)=0
See Also
Categories
Find more on Startup and Shutdown in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!