Hello,
The problem is that you need an array of points to plot a graph. I your code, x is an array but y is a scalar. Try this:
fprintf('Imp Euler With h=0.1')
dy=@(x,y) (x+y-1)^2;
f=@(x,y)(tan(x+(pi/4))-x+1);
x0=0;
h=0.1;
xn=0.5;
fprintf('x y(Imp. Euler) y(Actual) \n')
fprintf('%f\t %f\t %f\t \n',x0,y,f(x0));
x = x0:h:xn;
n = length(x);
y = zeros(1,n);
y(1) = 2;
for j = 1:n-1
i1=dy(x(j),y(j));
i2=dy(x(j+1),y(j)+(h*i1));
y(j+1) = y(j) + (h*((i1+i2)/2));
fprintf('%f\t %f\t %f\t \n',x(j),y(j),f(x));
end
plot(x,y,'r','linewidth',2);
hold on
legend ('Improved Euler');
