how can i write function to display matrix?

how can i write function to display a zero matrix and its diagonal calculated by function

f(n) = f(n-1)+2f(n-2)+3

it has only one input n

[Walter Roberson]

If you start with an all-zero matrix then every element of the matrix will be the same for any given n, so it seems odd to talk about the diagonal.

You would need a matrix multiplication step to perturb the elements so that the diagonals were not all the same.

Answer 1

[Masoud Dorvash]

Hello,

You just need to use

D = diag(v);

This command will create a matrix with the elements of v on the main diagonal.

Try to first create your v vector (here in your example is f(n)) then put it there.

v = [1 6 2 14 1 8 46];
diag(v)

ans =

     1     0     0     0     0     0     0
     0     6     0     0     0     0     0
     0     0     2     0     0     0     0
     0     0     0    14     0     0     0
     0     0     0     0     1     0     0
     0     0     0     0     0     8     0
     0     0     0     0     0     0    46