Problem with vpasolve after specifying range of solutions as [-Inf Inf]

1 次查看（过去 30 天）

显示更早的评论

Ash Ash 2018-6-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/406829-problem-with-vpasolve-after-specifying-range-of-solutions-as-inf-inf

评论： Ash Ash 2018-6-21

在 MATLAB Online 中打开

Hi, I seem to have encountered a weird problem with vpasolve when I specify a range of solutions.

I have 'a' defined as a symbolic variable.

After running the script below, 'test1' returned some real, non-trivial solutions from a1 to a4.

test1=vpasolve([a(1)*0.67 + a(4)*0.5 + a(2)*0.1 == 5 ; a(3)*0.3 + a(1)*2== 10])

However, after specifying, a range of solutions for vpasolve(), it returned empty 0x1 sym results in 'test2'

test2=vpasolve([a(1)*0.67 + a(4)*0.5 + a(2)*0.1 == 5 ; a(3)*0.3 + a(1)*2== 10], [a(1:4)],[-inf,inf;-inf,inf;-inf,inf;-inf,inf])

For another test case, I gave vpasolve a different equation with a similar format of having 4 unknowns shown below, but somehow 'test3' was able to return some non-trivial solutions.

test3=vpasolve([a(1)*sin(10*a(4)) + a(2)^3 == 5 ; a(3)^2 + exp(-2*a(1)/3)== 10], [a(1:4)],[-inf,inf;-inf,inf;-inf,inf;-inf,inf])

Would you please help me understand why is this the case? How can I make 'test2' return the same results as 'test1'?

Thank you very much for your time.

7 个评论
显示 5更早的评论隐藏 5更早的评论

Walter Roberson 2018-6-21

solve() and vpasolve() are the only symbolic solvers that there is direct access to.

If you are willing to go into MuPAD then there are https://www.mathworks.com/help/symbolic/mupad_ref/linsolve.html and https://www.mathworks.com/help/symbolic/numeric-solvers.html . Note that you need to either "mupad" to use these, or invoke dark rituals involving evalin(symengine).

Ash Ash 2018-6-21

Hahaha I have no experience with MUPAD and hilarious as "invoke dark rituals" sound, I hope you understand that I'm trying not to make this more difficult than it should be.

Might you have another suggestion?

Something similar to using a matrix like "lsqlin" perhaps? I can use "equationsToMatrix" so something like this would also be acceptable.

Thank you once again.

请先登录，再进行评论。

请先登录，再回答此问题。