How to graph dashed reference line at 0?

I can't figure out how to graph a dashed line at 0 through the end of the graph (which would represent the ground). Currently the script I have is:

clear
clc

h=1.5; %m, height of ball at release

g=9.8; %m/s/s, gravity

%ask users for v and angle inputs
v=input('Enter velocity of ball at release:');

theta=input('Enter angle of ball at release:');

t=linspace(0,1,1000);%interval for 1 sec

x=v*cos(theta*(pi/180))*t; %formula for distance

y=h+(v*(sin(theta*(pi/180))))*t-(.5*g*t.^2); %formula for when height=0

x1=find(y<0);%assigns x1 the value of the vector list for when y<0

distance=x(x1(1)); %calculates x at when y=0

%Display answer to user
fprintf('The ball hits the ground at a distance of %d meters.\n', distance)

xlabel('Distance travelled (m)')

ylabel('Height travelled (m)')

title('Trajectory of Ball')

plot(x,y)

hold on

plot([0,0],[v,0], '--')

Answer 1

[Walter Roberson]

xL = get(gca, 'XLim');
plot(xL, [0 0], '--')

Remember, the ground is a height and height is Y rather than X.

The bit about getting the XLim is finding the left and right margins of what you currently have plotted; then the plot command plots a line across from the left to right margin.