how to create nxn matrix with main diagonal that enters odd rows/columns with zero and even ones start with 2(n+1) sequence

Question

Lama 2024-5-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2119126-how-to-create-nxn-matrix-with-main-diagonal-that-enters-odd-rows-columns-with-zero-and-even-ones-sta

回答： John D'Errico 2024-5-15

im trying to write a code where even main diagonal entries start off with 2 and continue 4,6,8.... etc but i only get outputs of 2. im assuming my problem is with the n=n+1 counter but im not sure.

my code is = for i=1:30;

For j=1:30;

for i=j

c=1;

if mod(i,2)~0 A(i,j)=2*c c=c+1; if mod (i, 2) ==0

A(i, j)=0;

end

end end

end

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Answer 1

Torsten 2024-5-15

移动：Torsten 2024-5-15

在 MATLAB Online 中打开

n=10;
A=zeros(n);
for i=2:2:n
    A(i,i) = i;
end
A
A = 10x10
     0     0     0     0     0     0     0     0     0     0
     0     2     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     4     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     6     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     8     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0    10
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Answer 2

John D'Errico 2024-5-15

在 MATLAB Online 中打开

Simple is to use diag.

n = 5; % Now many non-zero elements will we have?
N = 1:(2*n); % a simple index vector
D = N.*mod(N-1,2); % create the elements of the main diagonal
A = diag(D)
A = 10x10
     0     0     0     0     0     0     0     0     0     0
     0     2     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     4     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     6     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     8     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0    10
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