99x99 matrix

create a 99x99 matrix with ones on both diagonals and zeros everywhere otherwise

Answer 1

[Image Analyst]

Another way, even more compact:

A = eye(99) | fliplr(eye(99))

As long as it's not your homework you can use my code.

[C B]

great wayorring flip i liked it

Answer 2

[Chunru]

n = 9;  %99
A = eye(n);
A(n:n-1:n*n-1) = 1;  % anti-diagonal
A

A = 9×9

1 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 1

Answer 3

[Image Analyst]

As long as it's not your homework you can use my code:

A = min(1, eye(99) + fliplr(eye(99)))

Answer 4

[Chunru]

% For time comparison:
n = 1000;
timeit(@() bidiag1(n))

ans = 4.1086e-04

timeit(@() bidiag2(n))

ans = 0.0027

timeit(@() bidiag3(n))

ans = 0.0019

function bidiag1(n)
a = eye(n);
a(n:n-1:n*n-1) = 1;
end

function bidiag2(n)
a = eye(n) | fliplr(eye(n));
end

function bidiag3(n)
a = min(1, eye(n) + fliplr(eye(n)));
end