YALMIP is returning that a program is infeasible

[Hann]

down votefavorite

I'm having a problem trying to use YALMIP (https://yalmip.github.io/?n=Main.HomePage); I want to solve an LMI with Yalmip Here's the code: x1 = sdpvar(1, 1) x2 = sdpvar(1, 1) L= lmi(-[1-x1 x1+x2 x1; x1+x2 2-x2 0; x1 0 1+x2]) Z= solvesdp(L,[ ]) but it returns : info: 'Infeasible problem (SeDuMi-1.3)' problem: 1 why and how can I solve this problem? and another question: when I used plot(L) it only shows the final answer, how can I plot all principal minors of it?

[Johan Löfberg]

Well, it is infeasible, so there is not much to do. Neither can you solve it, nor can you plot the feasible set as it is empty

You are using a syntax which is very obsolete

https://yalmip.github.io/tutorial/basics/

I suspect you've switched the sign, since with reversed sign it is feasible

L = [1-x1 x1+x2 x1; x1+x2 2-x2 0; x1 0 1+x2] >= 0

plot(L)

optimize(L)
value([x1 x2])

[Hann]

Thank you so Much, Johan 

 I have another question, how can I Plot Principle minors of L?

[Johan Löfberg]

The priniple minors are functions. YALMIP does not plot functions, but plots feasible sets. If you want to plot polynomial functions, you will have to use tools such as ezplot etc