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Plotting the area defin

Asked by Sultan Al-Hammadi on 13 Oct 2018
Latest activity Edited by Sultan Al-Hammadi on 15 Oct 2018
Iluating x & y, I don't want a & b to be always the same as long as 0<=a<=1 & 0<=b<=1. But I have no idea to resolve this issue!!


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3 Answers

Answer by John D'Errico
on 13 Oct 2018

You know how to use meshgrid! In fact, I know that, because you used it in your other question.
So it you want to plot something over all combinations of a and b, then why not use meshgrid? (10000 points in each dimensions will be wild overkill of course.)


You need to be clear in what you want to do? Still your statement is not clear
As I said, you resolve the issue by using meshgrid. meshgrid generates ALL combinations of the two variables, a & b.
[a,b] = meshgrid(0:.01:1,0:.01:1);
So a and b are now TWO dimensional arrays, here, each of size 101x101. Now compute x and y as directed.
x = a.^2 - b.^2;
y = a.*b;
The result is a sort of triangular domain, with curved edges along the top.
Are you asking how to generate the boundary of that domain? From what you have said, I don't think so.
edgeind = convhull(x(:),y(:));
But you need to understand that when you want to generate all combinations of two variables like this, USE MESHGRID.
Thank you so much, it looks quite right

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Answer by Bruno Luong
on 13 Oct 2018
Edited by Bruno Luong
on 13 Oct 2018

almost right, you need to make a & b oriented in 2 different dimensions (here row for a and column for b)
b=linspace(0,1,101)'; % <= make a column


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you do not need to have same a and b, simply make them oriented differently
Is there a way to get it every possible value of a & b, and hence evaluating all possible values of x & y? [for example, a could equal to 0.1 while b=1, etc]
??? x, y are already computed from all combination of a, b with resolutions of 0.01.
So what your question is about? Might be your should slow down think, then ask a real question.

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Answer by Bruno Luong
on 13 Oct 2018

Or perhaps you want this?
rect = [a 0+0*a;
1+0*b b;
flip(a) 1+0*a;
0+0*b flip(b)];
a = rect(:,1);
b = rect(:,2);


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