Display radius on the plot

%% 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

Answer 1

[Star Strider]

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.

[jeet Mehta]

thanks for that , i have fixed the axis and have define it is showing the line. But also if i wana display the radius at the circle saying it is R=1.5 or any values how do i do it .

% text(xra(1,45), yra(2,45), '$R\ =\ 1.5$','Interpreter','latex')

% text(xra(1,120), yra(1,120), '$R\ =\ 2.0$','Interpreter','latex')

I have tried this and it dosent work . Please guide

[jeet Mehta]

@star strider

[Star Strider]

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]

Thank you i did relaised that and fixed it yesterday . Thanks heaps really appreciate

[Star Strider]

As always, my pleasure.

Answer 2

[KSSV]

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]

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

[KSSV]

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