svm-plot.m

 alphas = find(xPD>0.0001);
 W=sum(xPD(alphas,:).*y(alphas,:).*x(alphas,:))
 bias =mean( y(alphas,:) - x(alphas,:)*W')
%  Xsupport=x((find(xPD~=0)),:);
% Ysupport=y((find(xPD~=0)),:);
Xsupport=x(alphas,:);
Ysupport=y(alphas,:);

hold on
scatter(x(y==1,1),x(y==1,2),'b')
scatter(x(y==-1,1),x(y==-1,2),'r')
scatter(Xsupport(Ysupport==1,1),Xsupport(Ysupport==1,2),'.b')
scatter(Xsupport(Ysupport==-1,1),Xsupport(Ysupport==-1,2),'.r')
syms x1 x2
fn=vpa((-bias-W(1)*x1)/W(2),6);
fn1=vpa((-1-bias-W(1)*x1)/W(2),6);
fn2=vpa((1-bias-W(1)*x1)/W(2),6);
fplot(fn,'Linewidth',3);
fplot(fn1,'Linewidth',1,'Color','g', 'LineStyle', '--');
fplot(fn2,'Linewidth',1,'Color','g', 'LineStyle', '--');

legend('Positive class', 'Negative Class', 'Support Vectors', 'Support Vectors', 'Decision Boundary', 'Margins', 'Location', 'best')
xlabel ('x1')
ylabel('y1')
hold off