# Moving point with fixed distance and random direction

8 views (last 30 days)
Hon Man LAU on 3 Nov 2019
Hi guys. I am doing simulation of user distribution. I have generated some random points to represent the users.
But now, I want to make the points move so that the users are walking with constant speed.
I want to make moving points animiation with
• Fixed distance (distance between point A and point B = point B to point C)
• Random direction
And I want to record all the coordinates of points. Thank you.
Daniel M on 3 Nov 2019
Edited: Daniel M on 3 Nov 2019
Are you saying you have user 1 at point A and you want the coordinates of all possible points to a fixed distance point B? That would just be the surface of a sphere with radius B and origin A.
Adam Danz on 3 Nov 2019
Edited: Adam Danz on 3 Nov 2019
Perhaps an illustration would help to define the problem.
"If I had only one hour to save the world, I would spend fifty-five minutes defining the problem, and only five minutes finding the solution." -Albert Einstein

Neeraj Rajpurohit on 7 Apr 2021
DISCLAIMER: These are my own views and in no way depict those of MathWorks.
Greeings,
The following code might help you get started. It shows 10 users moving in random directions with a constant velocity. Note that I used ‘findobj’ and ‘set’ functions to get update plot coordinates. Please find the relevant documentation link below.
clear;
hold off;
box on;
users = 10;
xValues = uint8(rand(1,users) * 100);
yValues = uint8(rand(1,users) * 100);
xdValues = uint8(rand(1,users) * 100);
ydValues = uint8(rand(1,users) * 100);
rt = scatter(yValues, xValues, 'blue');
xlabel('size');
ylabel('size');
axis([0 100 0 100]);
step_size = 1;
while 1
y_t = double(ydValues)-double(yValues);
x_t = double(xdValues)-double(xValues);
x = zeros(1,users);
y = zeros(1,users);
for i=1:users
if(x_t(i) == 0)
y(i) = double(yValues(i))+ sign(y_t(i)) * step_size;
else
m = y_t(i)./x_t(i);
sine = m./sqrt(1+m.^2);
cosine = 1./sqrt(1+m.^2);
x(i) = double(xValues(i)) + cosine.*sign(x_t(i))*step_size;
y(i) = double(yValues(i))+ (abs(sine) .* sign(y_t(i))) * step_size;
end
end
xValues = x;
yValues = y;
d = sqrt(y_t.^2 + x_t.^2);
h = findobj(rt);
pause(.23);
prevX = get(h,'XData');
prevY = get(h,'YData');
set(h,'XData',xValues);
set(h,'YData',yValues);
end