How can I can I create a square diagonal matrix and insert variables into it?

Hello,

I need to create a 500x500 matrix that looks like this

[0 0 0 0 0 x 
 0 0 0 0 x 0
 0 0 0 x 0 0
 0 0 y 0 0 0
 0 y 0 0 0 0
 y 0 0 0 0 0 ]
now i know that i can use eye(0,0) command and use the fliplr() to create an inverse identity matrix. but i just need to know how to add variables into it.....
any ideas?
your help is appreciated
THANK YOU :)

[Amit]

Does only half the values are x and rest y in the diagonal matrix?

[Anas]

Yes that is exactly right :)

Answer 1

[Azzi Abdelmalek]

   A=zeros(6)
 [n,m]=size(A);
 idx=sub2ind([n m],1:n,n:-1:1)
 x=5;
 y=10;
 A(idx)=[x x x y y y ]

[Anas]

thank you Azzi... but I need to do this on a 500x500 matrix.. is there a way?? thanks for your help :)

[Azzi Abdelmalek]

A=zeros(500)
[n,m]=size(A);
idx=sub2ind([n m],1:n,n:-1:1)
x=5;
y=10;
A(idx)=[repmat(x,1,250) repmat(y,1,250) ]

[Anas]

thanks a lot Azzi :)

Answer 2

[Bjorn Gustavsson]

Unless you need something outlandishly fast or special I'd go for KISS:

M = flipud(diag([y y y y x x x x]));

HTH

[Anas]

Thanks a lot :)

[Anas]

Thats a great one björn. is it possible to do it for a 500x500 matrix?? thank you

[Azzi Abdelmalek]

Using Bjorn code

M = flipud(diag([repmat(x,1,250) repmat(y,1,250)]));

[Anas]

Thanks Azzi :)