tril
Syntax
tril(X, [k=0])
Arguments
X is a matrix.
k (optional) is an integer.
Details
If k is not specified: return the lower triangular portion of matrix X.
If k is specified: return the elements on and below the k-th diagonal of X.
Examples
m=matrix(1 2 3, 4 5 6, 7 8 9);
m;| col1 | col2 | col3 |
|---|---|---|
| 1 | 4 | 7 |
| 2 | 5 | 8 |
| 3 | 6 | 9 |
tril(m);| col1 | col2 | col3 |
|---|---|---|
| 1 | 0 | 0 |
| 2 | 5 | 0 |
| 3 | 6 | 9 |
tril(m,1);| col1 | col2 | col3 |
|---|---|---|
| 1 | 4 | 0 |
| 2 | 5 | 8 |
| 3 | 6 | 9 |
tril(m,-1);| col1 | col2 | col3 |
|---|---|---|
| 0 | 0 | 0 |
| 2 | 0 | 0 |
| 3 | 6 | 0 |
Related function: triu