a simple substitution problem !

i have a 2x2 matrix

u = [ 10 10 ; 5 5 ] ; for example

how can i use a simple code to transfer it to

u =

[ 0.5 10 ; 5 0.5 ]

i use

subs ( diag(u) , 0.5 );

but it didn't work

please help me with the problem!!!

thank you!

Answer 1

[Azzi Abdelmalek]

Edit

u = [ 10 10 ; 5 5 ];
y=u(:);
n=size(u,1);
y((1:n).^2)=0.5;
out=reshape(y,n,n)

Answer 2

[José-Luis]

a = rand(10);
[m n] = size(a);
a(1:m+1:numel(a)) = 0.5;

Answer 3

[Andrei Bobrov]

a = rand(10);
a(eye(size(a))>0) = 0.5;