How do i create a (n x n) matrix using algorithm or other way whose elements are either -1, +3, –3 & 1 , otherwise 0, such that a11=a22=a33=.....=-1, a12=a23=a34=.....= 3, a13=a24=a35=.......= -3, a14=a25=a36=....= 1,.

How do i create a (n x n) matrix using algorithm or other way, whose elements are either -1, +3, –3 & 1 ,such that a11=a22=a33=.....=-1, a12 = a23 = a34 =.....= 3, a13 = a24 = a35=.......= -3, a14 = a25 = a36 =....= 1,otherwise 0.

[Shivangi Chauhan]

How is it possible for mxn matrix? for m=12 & n=15?

Answer 1

[Stephen23]

You can use toeplitz:

>> N = 6;
>> toeplitz([-1,zeros(1,N-1)],[-1,3,-3,1,zeros(1,N-4)])
ans =
    -1     3    -3     1     0     0
     0    -1     3    -3     1     0
     0     0    -1     3    -3     1
     0     0     0    -1     3    -3
     0     0     0     0    -1     3
     0     0     0     0     0    -1

If N can be less than four, then you will need to do this:

>> N = 3;
>> C = [-1,3,-3,1,zeros(1,N-4)];
>> R = [-1,zeros(1,N-1)];
>> toeplitz(R(1:N),C(1:N))
ans =
    -1     3    -3
     0    -1     3
     0     0    -1

[Stephen23]

It is trivial to make this work with non-square matrices:

>> M = 5;
>> N = 7;
>> toeplitz([-1,zeros(1,M-1)],[-1,3,-3,1,zeros(1,N-4)])
ans =
    -1     3    -3     1     0     0     0
     0    -1     3    -3     1     0     0
     0     0    -1     3    -3     1     0
     0     0     0    -1     3    -3     1
     0     0     0     0    -1     3    -3