Concerned that matlabFunction( ), when converting from symbolic to numerical, changes the sizes of matrices and vectors,

2 次查看（过去 30 天）

显示更早的评论

Noob 2024-11-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2168988-concerned-that-matlabfunction-when-converting-from-symbolic-to-numerical-changes-the-sizes-of-m

评论： Noob 2024-11-27

采纳的回答： Torsten

在 MATLAB Online 中打开

Hi there!

I am currently concerned that the function matlabFunction( ), when converting from symbolic to numerical, changes the sizes of matrices and vectors. For instance, I started with a 3x3 symbolic matrix M, gotten from equationsToMatrix( ). Then, I simplified this matrix using simplify( ). And, finally, I used matlabFunction to convert from symbolic to numerical, and to write the numerical matrix to a separate file. Now, when I go to check this separate file that's generated by Matlab, here is the last line, which gives the matrix M, and, it doesn't look 3x3 anymore. Does matlabFunction change the size of symbolic matrices and vectors, when converting from symbolic to numerical? If so, how can I preserve the original sizes of the symbolic matrices and vectors, after the conversion to numerical? Please see M below, generated by Matlab; it looks maybe 2x2 now, but I can't be sure. I don't know the 'reshape' command that Matlab used. But, it kind of looks 2x2, and, perhaps certainly, no longer 3x3. That is weird.

Another example is that my 3x1 vector 'b' no longer looks 3x1; it now looks 2x1, generated by Matlab.

Any help is greatly appreciated; thanks in advance!

mt1 = [(af.*m_perp_added.*(t26.*sin(t45)-1.0))./2.0-m_parallel_added.*t3.*t18.*t48+FD.*t2.*t18.*t47.*t53+FL.*t2.*t18.*t50.*t53;g.*(m_D+m_wing)-(af.*m_perp_added.*(t26.*cos(t45)+1.0))./2.0-V.*g.*rho_f-m_parallel_added.*t4.*t18.*t48+FD.*t2.*t18.*t50.*t53-FL.*t2.*t18.*t47.*t53];
mt2 = [(A.*omega.*rho_f.*w.^3.*abs(omega))./1.28e+2-t2.*t18.*t53.*(-yG+t18.*(m_D.*yG+m_wing.*yG-d_CD.*m_D.*t4)+(t2.*t18.*t56.*w.*(t6+t8+t25+t5.*t15-t6.*t14+t7.*t15-t8.*t14+t9.*t14+t15.*t25))./8.0).*(-t16+t31+FD.*t5+FD.*t7+FD.*t30+FL.*t6+FL.*t8+FL.*t40)-t2.*t18.*t53.*(-xG+t18.*(m_D.*xG+m_wing.*xG-d_CD.*m_D.*t3)+(t2.*t3.*t18.*t56.*w.*(t21+t22+t23+t24+t3.*t25+t4.*t25))./4.0).*(t16+t31-FD.*t6-FD.*t8+FD.*t29+FL.*t5+FL.*t7+FL.*t30)-V.*g.*m_D.*rho_f.*t18.*(xG-d_CD.*t3)];
b = [mt1;mt2];
M = reshape([-t4.*t12.*(m_parallel_added+m_wing+t13+t8.*t11),t22,0.0,t22,-t4.*t12.*(m_perp_added+m_wing-t13+t14),0.0,m_D.*m_perp_added.*t12.*t17,m_D.*m_perp_added.*t9.*t12,-m_D.*(t20+t21)-t12.*(t5.*t20+t5.*t21)-(m_wing.*(h.^2+w.^2))./1.2e+1],[3,3]);