test1.m

tm=10;
dt=0.01;
ta=0:dt:tm;
Lta=length(ta);

d0=0.01; % distance of stability
ss=0.03; % square size
m=1e-3;
k=1;
fcr=2*sqrt(k/m); % critical friction coeffcient
f=2*fcr; % friction coeficent


r=zeros(2,0);
g=[0; -10]; % gravitation

R=0.1;
R2=R^2;
ph=-0.1; % plate level
% make circle:
for yt=-R:d0:R
    for xt=-R:d0:R
        if (xt^2+yt^2<=R2)
            r=[r [xt;yt]];
        end
    end
end
hr=plot(r(1,:),r(2,:),'k.');
hold on;
hpl=plot([-0.15 0.15],ph*[1 1],'r--');
axis equal;

v=zeros(size(r)); % velocity
N=size(r,2);
Na=1:N;

for tc=2:Lta
    t=ta(tc);
    for n=Na
        rt=r(:,n);
        ft=find((abs(rt(1)-r(1,:))<=ss)&(abs(rt(2)-r(2,:))<=ss)&(n~=Na)); % rest points in square
        
    end
end