create a matrix with ones and zeros

in need to create an array of 20-by-20 the first row needs to be 19 ones and 1 zero the first column is all ones the last row is is all ones from the first row first column diagnally to the last row last column needs to be filled with ones, the rest are all zero.

now I can type this all out but there must be a better way

my question is how do i create this array?

Answer 1

[Star Strider]

This looks like what you want:

a = ones(1,20);
M = diag(a);
M(1,:) = [ones(1,19)  0];
M(:,1) = a';
M(20,:) = a;

[Tony Montgomery]

Thats awesome!! Im new to this so the help is much needed!! Thank you very much your awesome

[Star Strider]

My pleasure!

I just realised that I could have used ‘a’ in M(1:) as well:

M(1,:) = [a(1:19)  0];

[Tony Montgomery]

okay another problem close to the first.

need to create a similar array, but instead add variables.

so for example the last row need to be 19 of variable b and 1 one. how can i do that?