3x3 matrix with while loop

Question

Benjamin Trivers 2020-1-21

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https://ww2.mathworks.cn/matlabcentral/answers/501303-3x3-matrix-with-while-loop

评论： Jeremy 2020-1-21

Produce a random 3x3 matrix A that is invertible and display it. Hint: Use a while-loop until you get one with non-zero determinant. To create a random matrix with N rows and M columns,use the MATLAB command rand(N,M).

I know how to produce the 3x3 matrix and how to display it. I am just a little confused on how to use the while-loop. Can someone please help me?

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Alex Mcaulley 2020-1-21

在 MATLAB Online 中打开

determinant = 0;
while determinant == 0
    %Generate the random matrix
    %Calculate the determinant of that matrix
end

Benjamin Trivers 2020-1-21

I made a script for this one, and it just ran forever

I need it to stop if the determinate = 0

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Answer 1

Jeremy 2020-1-21

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https://ww2.mathworks.cn/matlabcentral/answers/501303-3x3-matrix-with-while-loop#answer_411251

在 MATLAB Online 中打开

n = 3; m = 3;
A = zeros(n,m);
while det(A) == 0
    A = rand(n,m);
end

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Benjamin Trivers 2020-1-21

just a little confused. the end of the question stated "Use disp to print matrices" so i thought i was looking for more than one matrix

sorry just confused

Jeremy 2020-1-21

在 MATLAB Online 中打开

Using rand, it's fairly unlikely that you'll create a matrix whose determinant is 0. It'd probably be easier to get a 0 determinant with randi

That being said, maybe running this will help you see what's going on

n = 3; m = 3;
A = zeros(n,m);
k = 0;
while det(A) == 0
    A = rand(n,m);
    k = k + 1;
    fprintf(1,'\nIteration Number %i \n',k)
    fprintf(1,' Matrix A = \n\n')
    disp(A)
    fprintf(1,'The Determinant of Matrix A is: \n')
    disp(det(A))
end

And if you wanted an (approximately) zero determinant:

n = 3; m = 3;
A = eye(n,m);
k = 0;
while abs(det(A)) > 0.001
    A = rand(n,m);
    k = k + 1;
    fprintf(1,'\nIteration Number %i \n',k)
    fprintf(1,' Matrix A = \n\n')
    disp(A)
    fprintf(1,'The Determinant of Matrix A is: \n')
    disp(det(A))
end

Using randi instead:

n = 3; m = 3;
A = eye(n,m);
k = 0;
while det(A) ~= 0
    A = randi([0 10],n,m);
    k = k + 1;
    fprintf(1,'\nIteration Number %i \n',k)
    fprintf(1,' Matrix A = \n\n')
    disp(A)
    fprintf(1,'The Determinant of Matrix A is: \n')
    disp(det(A))
end