Display radius on the plot

Asked by jeet Mehta

jeet Mehta (view profile)

on 11 Jun 2019
Latest activity Commented on by Star Strider

Star Strider (view profile)

on 11 Jun 2019
Accepted Answer by Star Strider

Star Strider (view profile)

%% Plot Region of Attraction
for k=1:360
xra(k)=2*cos(2*pi*k/360);
yra(k)=2*sin(2*pi*k/360);
end
figure(1)
p1=plot(xra,yra,'--r')
title('Initial Condition with radius ')
xlabel('x1(t)')
ylabel('x2(t)')
grid
axis(2.5*[-1 1 -1 1])
hold on
%% Plot Initial Circle
for k=1:360
xc(k)=ro*cos(2*pi*k/360); %Projection on x1
yc(k)=ro*sin(2*pi*k/360); %Projection on x2
end
figure(1)
p2=plot(xc,yc,'--k')
%% Run Simulation for N different initial conditions
for k =1:N
x1_o=ro*cos(2*pi*k/10+pi/6); %Projection on x1
x2_o=ro*sin(2*pi*k/10+pi/6); %Projection on x2
%% Simulation Linear Model
sim('sim_nonlinear_new.slx')
%states
x1=x(:,1);
x2=x(:,2);
scatter(x1_o,x2_o,100,'ok','filled') %Plot initial condition
plot(x1,x2) %Plot trajectory
drawnow;
legend([p1 p2],{'First','Second'});
end
hold off
I have above code for region of attraction circle and intial circle. I want to be able to display with a line drawing out and radius of the two circles. Please help

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Answer by Star Strider

Star Strider (view profile)

on 11 Jun 2019

You did not define ‘ro’.
When you do, you can plot the radius easily as:
plot([0 xra(45)], [0 yra(45)], '-b', [0 xc(135)],[0 yc(135)],'-g')
after the second loop. Choose whatever index you want to define the radius lines.
I would also use:
axis equal
so your circles don’t look like elipses.

Star Strider

Star Strider (view profile)

on 11 Jun 2019
As always, my pleasure.
I am not certain what doesn’t work, unless it is a problem with the LaTeX interpreter.
Also, you are plotting both radius values using the same circle designation (the ‘xra’, ‘yra’ circle).
Try this:
text(xc(1,45), yc(2,45), '\$R\ =\ 1.5\$','Interpreter','latex')
text(xra(1,120), yra(1,120), '\$R\ =\ 2.0\$','Interpreter','latex')
Without the LaTeX interpreter:
text(xc(1,45), yc(2,45), 'R = 1.5')
text(xra(1,120), yra(1,120), 'R = 2.0')
If you want to change to display a different radius, just edit the text within the single quotes.
jeet Mehta

jeet Mehta (view profile)

on 11 Jun 2019
Thank you i did relaised that and fixed it yesterday . Thanks heaps really appreciate
Star Strider

Star Strider (view profile)

on 11 Jun 2019
As always, my pleasure.

KSSV (view profile)

on 11 Jun 2019

YOu can display radius of the circle like below:
th = linspace(0,2*pi) ;
R = 1. ; % REadius of Circle
C = [0. 0.] ; % cneter of circle
x = C(1)+R*cos(th) ;
y = C(2)+R*sin(th) ;
plot(x,y)
hold on
plot([C(1) x(1)],[C(2) y(1)])

jeet Mehta

jeet Mehta (view profile)

on 11 Jun 2019
It giving me error saying its bound to index 1 . Can u please have a look at the code above and suggest
KSSV

KSSV (view profile)

on 11 Jun 2019
The above code doesn't show any error. It is wokring fine unless you make some changes.