Some famous Matrices
- Diagonal if \( a_{ij}=0 \) for \( i\ne j \)
- Upper triangular if \( a_{ij}=0 \) for \( i > j \)
- Lower triangular if \( a_{ij}=0 \) for \( i < j \)
- Upper Hessenberg if \( a_{ij}=0 \) for \( i > j+1 \)
- Lower Hessenberg if \( a_{ij}=0 \) for \( i < j+1 \)
- Tridiagonal if \( a_{ij}=0 \) for \( |i -j| > 1 \)
- Lower banded with bandwidth \( p \): \( a_{ij}=0 \) for \( i > j+p \)
- Upper banded with bandwidth \( p \): \( a_{ij}=0 \) for \( i < j+p \)
- Banded, block upper triangular, block lower triangular....