automatically filling a matrix

24 views (last 30 days)
bus14
bus14 on 22 May 2019
Edited: Stephen23 on 9 Aug 2019
Hi community,
n=200;
i=3;
j=6;
I want to create a matrix which fills a matrix of (n*j) x j and has in the first column -1 for the first n numbers and the rest zeros and for the second column n zeros,n -ones and for the rest zeros again.
I created one manually for the following situation of n=200;i=3;j=6; However, I want to create a script in which I can increase the values of n,i,j and Matlab automatically generates a new correct matrix. Does anyone know how to do this?
My own code is
% when n=200; i=3; and j=6;
AX1= [-ones(n,1);zeros(5*n,1)];
AX2= [zeros(n,1);-ones(n,1);zeros(4*n,1)];
AX3= [zeros(2*n,1);-ones(n,1);zeros(3*n,1)];
AX4= [zeros(3*n,1);-ones(n,1);zeros(2*n,1)];
AX5= [zeros(4*n,1);-ones(n,1);zeros(n,1)];
AX6= [zeros(5*n,1);-ones(n,1)];
AX=[AX1,AX2,AX3,AX4,AX5,AX6];
Thanks in advance!

Accepted Answer

Stephen23
Stephen23 on 22 May 2019
Edited: Stephen23 on 9 Aug 2019
Method one: eye and kron:
>> n = 5;
>> j = 6;
>> M = kron(-eye(j),ones(n,1))
M =
-1 0 0 0 0 0
-1 0 0 0 0 0
-1 0 0 0 0 0
-1 0 0 0 0 0
-1 0 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 0 -1
0 0 0 0 0 -1
0 0 0 0 0 -1
0 0 0 0 0 -1
0 0 0 0 0 -1
Method two: eye and repelem:
>> M = repelem(-eye(j),n,1)
M =
-1 0 0 0 0 0
-1 0 0 0 0 0
-1 0 0 0 0 0
-1 0 0 0 0 0
-1 0 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 0 -1
0 0 0 0 0 -1
0 0 0 0 0 -1
0 0 0 0 0 -1
0 0 0 0 0 -1
Method three: blkdiag and a comma separated list:
>> C = {-ones(n,1)};
>> M = blkdiag(C{ones(1,j)})
M =
-1 0 0 0 0 0
-1 0 0 0 0 0
-1 0 0 0 0 0
-1 0 0 0 0 0
-1 0 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 -1 0 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 -1 0 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 -1 0 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 -1 0
0 0 0 0 0 -1
0 0 0 0 0 -1
0 0 0 0 0 -1
0 0 0 0 0 -1
0 0 0 0 0 -1
  1 Comment
bus14
bus14 on 22 May 2019
Great thanks for your help

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!