problem with determinant calculus

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zini giacomo 2018-2-8

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https://ww2.mathworks.cn/matlabcentral/answers/381472-problem-with-determinant-calculus

评论： Aveek Podder 2018-2-20

i've a problem in the calculus of the determinant of a matrix, which his components change in the time, the determinant calculated in the analytic way and with 'det' function results different.

function [w1,w]=singular5(q1,q2,t)
time=size(t);
time=time(2);
w=zeros(1,time);
w1=zeros(1,time);
for k=1:time
J=[-(sin(q1(k)+sin(q1(k)+q2(k)))) -sin(q2(k)) 0 0;-(cos(q1(k)+cos(q1(k)+q2(k)))) -cos(q2(k)) 0 0;0 0 1 0;1 1 0 1];
w1(k)=abs(sin(q1(k)-q2(k))+sin(q1(k)));
 w(k)=abs(det(J));
 end
  % code
w1 and w result differnet!

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zini giacomo 2018-2-8

Oops i've miss some parentesis

Aveek Podder 2018-2-20

在 MATLAB Online 中打开

Hi,

Hope this helps:

function [w1,w]=singular5(q1,q2,t)
time=size(t);
time=time(2);
w=zeros(1,time);
w1=zeros(1,time);
for k=1:time
    J=[-(sin(q1(k))+sin(q1(k)+q2(k))) -sin(q2(k)) 0 0;-(cos(q1(k))+cos(q1(k)+q2(k))) -cos(q2(k)) 0 0;0 0 1 0;1 1 0 1];
    w1(k)=abs(sin(q1(k)-q2(k))+sin(q1(k)));
    w(k)=abs(det(J));
end