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How do I draw the arrow like in the first picture(the targeted phase-plane portraits )?

the targeted phase-plane portraits

my phase-plane portraits

Attached is the code for my phase portraits.

Orion
on 6 Nov 2014

Hi,

Modifying your script phase_plane_example5, you could do something something like

clear

clc

X = [];

Y = [];

U = [];

V = [];

color = 'mrb';

for i=0:10:60

for j=-5:5:5

b = i;

a = j;

k = j/5+2;

[t,x] = ode45('mpac',0:0.01:10,[a/57.3;b/57.3]);

plot(a,b,'*k');

hold on;

plot(x(:,1)*57.3,x(:,2)*57.3,color(k));

% stock the positions.

X = [X,x(:,1)*57.3];

Y = [Y,x(:,2)*57.3];

% calculate and stock the derivatives.

U = [U,diff(x(:,1)*57.3)./diff(t)];

V = [V,diff(x(:,2)*57.3)./diff(t)];

end

end

title('Phase plane plot of roll dynamics');

xlabel('Roll angle(deg)');

ylabel('Roll rate(deg/s)');

grid on;

% add an initial line of values to the derivatives terms to have the same

% length vectors and match the position ones.

U=[zeros(1,21);U];

V=[zeros(1,21);V];

% draw the arrows.

quiver(X,Y,U,V);

Orion
on 7 Nov 2014

1) I inversed my concatenation : you must use

U=[U;zeros(1,21)];

V=[V;zeros(1,21)];

zeros is just used here to make the speed vectors of the same size of the position vectors.

2) if you want to play with the propoerties of the quiver plot (size for example)

q = quiver(X,Y,U,V);

set(q,'AutoScaleFactor',6);

as a result

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