problem in inserting a diagnol

hi, i have a problem in inserting the diagnol of a matrix. i have a=[1 2 3;4 5 6;7 8 9] in which i have to extract the diagnol by multiplying with 2 and i want to again insert the diagnol i,e iwant to have [2 2 3;4 10 6;7 8 18]; i dont want to use the loop.

[the cyclist]

Seems like a homework problem. What have you tried already? (Also, should that 27 actually be an 18?)

[Yash]

how do u want the output to be

[San]

he want to have double for diagonal but don't want loop :(

Answer 1

[Conrad]

A = [   1 2 3;...
        4 5 6;...
        7 8 9];
A(1:(length(A)+1):numel(A)) = 2*diag(A);