function demo_pca(d,N,sg,plotit);

%function demo_pca(d,N,sg,plotit);
colordef black

if nargin < 4
   plotit = 1;
end

if nargin < 3
   sg=0.1;
end
if nargin < 2
   N=200;
end
if nargin < 1
   d=1;
end


y=randn(d,N);
sgs=rand(3,1)*sg
n=(sgs*ones(1,N)).*randn(3,N);
A=rand(3,d)

x=A*y+n;


if d==2
   
xx=[-4 4];
xy=[0 0];
yx=[0 0];
yy=[-4 4];
Axx=A*[-4;0];
Axy=A*[4;0];
Ayx=A*[0;-4];
Ayy=A*[0;4];
 
XX=[Axx(1) Axy(1)];
XY=[Axx(2) Axy(2)];
XZ=[Axx(3) Axy(3)];
YX=[Ayx(1) Ayy(1)];
YY=[Ayx(2) Ayy(2)];
YZ=[Ayx(3) Ayy(3)];
W=[XX;XY;XZ;YX;YY;YZ];

else
   
   Ax=A*-4;
   Ay=A*4;
   
   X=[Ax(1) Ay(1)];
   Y=[Ax(2) Ay(2)];
   Z=[Ax(3) Ay(3)];
   W=[X;Y;Z];
   
   
end

figure(1);clf;
if d==1
   hist(y,30);
else
   plot(y(1,:),y(2,:),'y+','Markersize',2,'Linewidth',2);hold on;
if d==2
   plot(xx,xy,'m','LineWidth',2);
   plot(yx,yy,'m','Linewidth',2);hold off;
end   
end
   drawnow; pause;
   figure(2);clf;
   rotate3d on;
   plot3(x(1,:),x(2,:),x(3,:),'c+','Markersize',2,'Linewidth',2);hold on;
if d==2
   plot3(XX,XY,XZ,'m','LineWidth',2);
   plot3(YX,YY,YZ,'m','LineWidth',2);
  else
   plot3(X,Y,Z,'m','LineWidth',2);
end
    drawnow;
   
 pause  
 [A,Sig] = FA(x,d,plotit,W)
if d==2
   
Axx=A*[-4;0];
Axy=A*[4;0];
Ayx=A*[0;-4];
Ayy=A*[0;4];
 
XX=[Axx(1) Axy(1)];
XY=[Axx(2) Axy(2)];
XZ=[Axx(3) Axy(3)];
YX=[Ayx(1) Ayy(1)];
YY=[Ayx(2) Ayy(2)];
YZ=[Ayx(3) Ayy(3)];

else
   
   Ax=A*-4;
   Ay=A*4;
   
   X=[Ax(1) Ay(1)];
   Y=[Ax(2) Ay(2)];
   Z=[Ax(3) Ay(3)];
end

figure(2);
rotate3d on;
   %plot3(x(1,:),x(2,:),x(3,:),'c+','Markersize',2,'Linewidth',2);hold on;    
  if d==2
   plot3(XX,XY,XZ,'r','LineWidth',3);
   plot3(YX,YY,YZ,'r','LineWidth',3);
  else
   plot3(X,Y,Z,'r','LineWidth',3);
end
    drawnow;