function [x,y]=EulerTest(xstart,ystart,xend,n)
%This test function uses Euler's method to solve the ODE
%dy/dx = - y ^2  from  xstart  to  xend .
hstep=(xend-xstart)/(n-1);
x=zeros(n,1);
for j=1:n
    x(j)=xstart+(j-1)*hstep;
end
y=zeros(n,1);
y(1)=ystart;
for j=1:n-1
    y(j+1)=y(j)-hstep*(y(j))^2;
end
%Plot the exact solution  y = ystart/(1+ystart*(x - xstart)) .
xexact=[xstart:0.02:xend]';
yexact=ystart./(1+ystart*(xexact-xstart));
plot(xexact,yexact,'r')
hold on
%Plot the approximate solution in blue spots.
plot(x,y,'bo')
hold off