# Extend a matrix diagonally

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WARRIOR24 on 24 Mar 2021
Edited: Matt J on 24 Mar 2021
I am trying to exted a 4 x 4 matrix to... lets say a 9 x 9 matrix while keeping the diagonal numbers. BUT the 9 x 9 matrix can easily be changed to 11 x 11 and so and so on. I looking for a for loop that will be to scale this matrix depending on input numbers.
2 1 0 0
1 2 1 0
0 1 2 1
0 0 1 2
2 1 0 0 0 0 0 0 0
1 2 1 0 0 0 0 0 0
0 1 2 1 0 0 0 0 0
0 0 1 2 1 0 0 0 0
0 0 0 1 2 1 0 0 0
0 0 0 0 1 2 1 0 0
0 0 0 0 0 1 2 1 0
0 0 0 0 0 0 1 2 1
0 0 0 0 0 0 0 1 2

Matt J on 24 Mar 2021
Edited: Matt J on 24 Mar 2021
No need for a loop:
n=9;
result=toeplitz([2 1 zeros(1,n-2)])
result = 9×9
2 1 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 1 2
n=11;
result=toeplitz([2 1 zeros(1,n-2)])
result = 11×11
2 1 0 0 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 0 0 0 1 2 1

Matt J on 24 Mar 2021
Edited: Matt J on 24 Mar 2021

R2020b

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