Plot initial and final position only on plot

I'm making a time updated plot for a random walk simulation and I'm trying to do a plot showing the initial position only and another for the final position only. Does anyone have any ideas on how to do this I haven't been successful with my attempt of plotting (xa,ya)?

%Initial Position of A

xa = -5; xak = xa;

ya = 0; yak = ya;

%Initial Position of B

xb = 5; xbk = xb;

yb = 0; ybk = yb;

%Set a boundary position

BC = [5,-5,-5,5];

%Number of steps

nsteps = 5000;

%Set Collision Flag and Initial Step to Zero

collision_flag = 0; k = 0;

tic

while collision_flag == 0 && k < nsteps

[xakp1, yakp1] = RandWalk_2D(xak,yak,BC);

[xbkp1, ybkp1] = RandWalk_2D(xbk,ybk,BC);

%Create Particle A on Grid for Step(k)

xakval = [xak-.5, xak+.5, xak+.5, xak-.5];

yakval = [yak-.5, yak-.5, yak+.5, yak+.5];

%Create Particle A on Grid for Step(k+1)

xakvalp1 = [xakp1-.5, xakp1+.5, xakp1+.5, xakp1-.5];

yakvalp1 = [yakp1-.5, yakp1-.5, yakp1+.5, yakp1+.5];

%Create Particle B on Grid for Step(k)

xbkval = [xbk-.5, xbk+.5, xbk+.5, xbk-.5];

ybkval = [ybk-.5, ybk-.5, ybk+.5, ybk+.5];

%Create Particle B on Grid for Step(k+1)

xbkvalp1 = [xbkp1-.5, xbkp1+.5, xbkp1+.5, xbkp1-.5];

ybkvalp1 = [ybkp1-.5, ybkp1-.5, xbkp1+.5, ybkp1+.5];

figure(1)

hold on

xlim([-5.5,5.5,])

ylim([-5.5,5.5,])

fill(xa,ya,'r')

fill(xakval,yakval,'r') %current step A

fill(xakvalp1, yakvalp1, 'b')%next step for A

fill(xbkval,ybkval,'y') %current step B

fill(xbkvalp1, ybkvalp1, 'g')%next step for B

title('Initial Position of A and B')

%title('Final Position of A and B')

hold off

% if mod(nsteps,1000) == 0

% if collision_flag == 0

% break

% end

% end

%Update the New Position for Step(k+1)

xak = xakp1; yak = yakp1;

xbk = xbkp1; ybk = ybkp1;

k = k+1;

if xak == xbk && yak == ybk

collision_flag = 1;

niter = k;

end

end

Answer 1

[Alan Moses]

It is my understanding that you are trying to solve a collision problem in 2D plane. You can check out the scatter function to plot the initial and the final position. You can use the scatter function to plot the initial position before entering the loop, and by using hold on you can retain the current axes and use scatter once again to plot the final position on detecting collision.