我试图在MATLAB中找到符号3x3旋转矩阵的特征向量，它似乎适用于某些输入但不是全部，例如：
A =
[ cos(q), -sin(q), 0]
[ sin(q), cos(q), 0]
[ 0, 0, 1]
[V,lambda]=eig(A)
V =
[ 0, -i, i]
[ 0, 1, 1]
[ 1, 0, 0]
lambda =
[ 1, 0, 0]
[ 0, cos(q) - sin(q)*i, 0]
[ 0, 0, cos(q) + sin(q)*i]
这样可以正常工作，但是如果我尝试的不是围绕单位轴（x，y，z）的旋转，我会收到以下错误：
A =
[ cos(q), -sin(q), 0]
[ 0, 0, -1]
[ sin(q), cos(q), 0]
>> [V,lambda]=eig(A)
Warning: basis of eigenspace for eigenvalue cos(q)/3 - (cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 +
(cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3)/2 + (cos(q)/3 - cos(q)^2/9)/(2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 +
((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/... [linalg::eigenvectors]
??? Error using ==> mupadmex
Error in MuPAD command: Unable to find explicit eigenvectors.
Error in ==> sym.sym>sym.mupadmexnout at 2003
out = mupadmex(fcn,args{:});
Error in ==> sym.eig at 68
[V,D,p] = mupadmexnout('mllib::eigenvectors',A);
我正在使用特征值来找到矩阵的旋转轴，我需要将它用于更复杂的系统
任何帮助将不胜感激。 感谢
答案 0 :(得分：1)
我无法重现错误（在MATLAB R2010b上测试）：
syms q
A = [cos(q) -sin(q) 0 ; 0 0 -1 ; sin(q) cos(q) 0]
[V,lambda] = eig(A)
我得到以下（相当长的）结果：
A =
[ cos(q), -sin(q), 0]
[ 0, 0, -1]
[ sin(q), cos(q), 0]
V =
[ (3*cos(q)^2 + 4*cos(q)^3 + cos(q)^4 + 27*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(4/3) + 9*cos(q)*sin(q)^2 + 9*cos(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) - 6*cos(q)^2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3) + 9*cos(q)^2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) + 2*cos(q)^3*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3) + 18*cos(q)*(cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))/(3*sin(q)*(cos(q)^2 - 3*cos(q) + 9*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) + 3*cos(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3))*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3)), (3*cos(q)^2 - 27*3^(1/2)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(4/3)*i + 4*cos(q)^3 + cos(q)^4 + 27*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(4/3) + 9*cos(q)*sin(q)^2 - 18*cos(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) - 6*cos(q)^2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3) - 18*cos(q)^2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) + 2*cos(q)^3*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3) + 3*3^(1/2)*cos(q)^2*i + 4*3^(1/2)*cos(q)^3*i + 3^(1/2)*cos(q)^4*i + 18*cos(q)*(cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2) + 6*3^(1/2)*cos(q)^2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3)*i - 2*3^(1/2)*cos(q)^3*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3)*i + 18*3^(1/2)*cos(q)*(cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2)*i + 9*3^(1/2)*cos(q)*sin(q)^2*i)/(3*sin(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3)*(cos(q)^2 + 9*3^(1/2)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3)*i - 3*cos(q) + 9*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) - 6*cos(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3) + 3*3^(1/2)*cos(q)*i - 3^(1/2)*cos(q)^2*i)), -(27*3^(1/2)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(4/3)*i + 3*cos(q)^2 + 4*cos(q)^3 + cos(q)^4 + 27*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(4/3) + 9*cos(q)*sin(q)^2 - 18*cos(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) - 6*cos(q)^2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3) - 18*cos(q)^2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) + 2*cos(q)^3*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3) - 3*3^(1/2)*cos(q)^2*i - 4*3^(1/2)*cos(q)^3*i - 3^(1/2)*cos(q)^4*i + 18*cos(q)*(cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2) - 6*3^(1/2)*cos(q)^2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3)*i + 2*3^(1/2)*cos(q)^3*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3)*i - 18*3^(1/2)*cos(q)*(cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2)*i - 9*3^(1/2)*cos(q)*sin(q)^2*i)/(3*sin(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3)*(3*cos(q) + 9*3^(1/2)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3)*i - cos(q)^2 - 9*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) + 6*cos(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3) + 3*3^(1/2)*cos(q)*i - 3^(1/2)*cos(q)^2*i))]
[ -(9*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3))/(cos(q)^2 - 3*cos(q) + 9*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) + 3*cos(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3)), (18*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3))/(cos(q)^2 + 9*3^(1/2)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3)*i - 3*cos(q) + 9*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) - 6*cos(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3) + 3*3^(1/2)*cos(q)*i - 3^(1/2)*cos(q)^2*i), -(18*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3))/(3*cos(q) + 9*3^(1/2)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3)*i - cos(q)^2 - 9*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(2/3) + 6*cos(q)*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + (cos(q)^5/27 + (2*cos(q)^4)/27 + (cos(q)^3*sin(q)^2)/27 + cos(q)^3/27 + (cos(q)^2*sin(q)^2)/3 + sin(q)^4/4)^(1/2))^(1/3) + 3*3^(1/2)*cos(q)*i - 3^(1/2)*cos(q)^2*i)]
[ 1, 1, 1]
lambda =
[ cos(q)/3 + (cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3) - (cos(q)/3 - cos(q)^2/9)/(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3), 0, 0]
[ 0, cos(q)/3 - (cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3)/2 + (cos(q)/3 - cos(q)^2/9)/(2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3)) - (3^(1/2)*((cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3) + (cos(q)/3 - cos(q)^2/9)/(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3))*i)/2, 0]
[ 0, 0, cos(q)/3 - (cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3)/2 + (cos(q)/3 - cos(q)^2/9)/(2*(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3)) + (3^(1/2)*((cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3) + (cos(q)/3 - cos(q)^2/9)/(cos(q)^2/3 + cos(q)^3/27 + sin(q)^2/2 + ((cos(q)/3 - cos(q)^2/9)^3 + (cos(q)^3/27 + cos(q)^2/3 + sin(q)^2/2)^2)^(1/2))^(1/3))*i)/2]
答案 1 :(得分：0)
您给出的问题示例不是一般旋转矩阵，1不是特征值。点击此处查看http://en.wikipedia.org/wiki/Rotation_matrix。这不应该影响matlab函数，但是，保证了复数上的广义特征向量的基础。你有关于错误的更多信息吗？我注意到对基于对称矩阵的函数的一些调用，您是否尝试使用选项'qz'调用eig来显式调用基于非对称的算法？