Help plotting projectile motion

Ok, I have no idea what's wrong. I am awful at Matlab T_T. Anyway, it is plotting in yellow and it is not a parabola as I would have expected. Sorry and thanks in advance for any help.

if yh0 == 0

tmax = (2*yv0) / g; %Calculates the time of flight t = 2*Yvelocity / g    

for t = 1:0.01:tmax %When t is less than the time of flight keep looping

y_v(L) = y_v(L-1) + ( -g.*t );    
y_s(L) = ( y_v(L-1).*t ) + ( 1/2*-g.*t.^2 );

%Horizontal

x_v =  xv0;         %Horizontal doesn't change (acc=0)
x_s(L) =  xv0.*t;   %Horizontal displacement

L=L+1;

end

elseif yh0 > 0

      tmax = (yv0 / g) + (sqrt(((yv0)^2) + 2*g*yh0))/ g;

for t = 0:1:tmax %When t is less than the time of flight keep looping

L=L+1;               %Adds a counter each time the loop runs

y_v(L) = y_v(L-1) + g.*t;    %Calculates the Y velocity v = u+at
y_s(L) = y_v(L-1).*t + 1/2*g.*t.^2; %Calculates the Y displacement s = ut + 1/2at^2

%Horizontal

x_v    =  xv0;                           %Horizontal doesn't change (acc=0)
x_s(L) =  xv0.*t;                        %Horizontal displacement

MaxH= (v0^2 * sind(theta)^2 )/ 2*g;
end

end

%========================================================================%
%                                                                        %
%                           PLOTTING PROJECTILES                         %
%                                                                        %
%========================================================================%

figure %Opens in a new figure window
plot(x_s, y_s, 'ro', 'MarkerSize', 6, 'MarkerEdgeColor', [1 1 0], 'MarkerFacecolor', [.2 .2 1]);
title(' Projectile Motion ');    %Adds a title to the graph
xlabel(' Distance (M) ');        %Yup
ylabel(' Height (M) ');          %Is what it says

Answer 1

[Image Analyst]

Attached is my projectile demo. Perhaps that will help. It computes and plots just about everything you can imagine.

[Luke Oughton]

Thanks, I will give it a read and see what I can do with it. Appreciated.