how can i plot the arrows like in the targeted phase-plane portraits at the initial points?

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.

Answer 1

[Orion]

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);

[Xiwen Yuan]

hello Orion, thank you for your reply. It is very helpful to me,however,i still need your help because of the following two questions:

(1)I need only one arrow in each phase line at the initial point, like the targeted picture.

(2)According the modified script,the obtained arrows are very small(see figure below).how can i magnify their?

[Star Strider]

See Quiver Series Properties for details on how to modify the arrows.

[Orion]

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