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From: joey on 2 Aug 2010 03:33
Your problem is posed as...
>
> A = [1 -2 -1;1 0 0;1 .05 0];
> b = [1;0.186;-1.128];
> plotregion(A,b,[-200 -200 -200],[200 200 200])
>
> Note that since the set of inequalities you pose
> represents an infinite domain, I applied some bound
> constraints too. +/- 200 seemed wide enough here.
>
> So can you show what you tested, and what version
> of matlab you are running?
>



Hi there, I am unsure as to how they generated the b vector. I hope I am not hijacking the blog with this question. The reason why I am asking is I am trying to use plotregion for my own problem ( see http://www.mathworks.com/matlabcentral/newsreader/view_thread/288153#767059) and am very new to matlab.
I am trying to reverse engineer this explanation for A and b, so I can generate a graph for
z=(1-x-y)/(2-x-y)

if
K1-2K2>K3
K1>0.186
k1+0.05K2>-1.128

giving
A = [1 -2 -1;1 0 0;1 .05 0];
b = [1;0.186;-1.128];

implies to me that each row of the matrix is the LHS of one of the inequalities, while each, but then why is column 1 of b equal to 1, maybe it is just a typo, but just wanted to check as trying to work this out...
I am not sure how I can convert z into this form, but at least its a start.
Thank you
From: John D'Errico on 2 Aug 2010 06:53
"joey " <cansendifyouwantbutwontIgetspamifIpostmyemail?@gmail.com> wrote in message <i35sbi$7c7$1(a)fred.mathworks.com>...
> Your problem is posed as...
> >
> > A = [1 -2 -1;1 0 0;1 .05 0];
> > b = [1;0.186;-1.128];
> > plotregion(A,b,[-200 -200 -200],[200 200 200])
> >
> > Note that since the set of inequalities you pose
> > represents an infinite domain, I applied some bound
> > constraints too. +/- 200 seemed wide enough here.
> >
> > So can you show what you tested, and what version
> > of matlab you are running?
> >
>
>
>
> Hi there, I am unsure as to how they generated the b vector. I hope I am not hijacking the blog with this question. The reason why I am asking is I am trying to use plotregion for my own problem ( see http://www.mathworks.com/matlabcentral/newsreader/view_thread/288153#767059) and am very new to matlab.
> I am trying to reverse engineer this explanation for A and b, so I can generate a graph for
> z=(1-x-y)/(2-x-y)
>
> if
> K1-2K2>K3
> K1>0.186
> k1+0.05K2>-1.128
>
> giving
> A = [1 -2 -1;1 0 0;1 .05 0];
> b = [1;0.186;-1.128];
>
> implies to me that each row of the matrix is the LHS of one of the inequalities, while each, but then why is column 1 of b equal to 1, maybe it is just a typo, but just wanted to check as trying to work this out...
> I am not sure how I can convert z into this form, but at least its a start.

No. It was definitely not a typo!

What is 1*z ? (A hint: 1*z = z)

And why do you think that plotregion can plot a
general nonlinear surface? It is not designed to do
anything of the sort.

help ezsurf

John
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