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# trilower()

Usage:
 ```trilower(A), A a matrix ```

Keywords: matrix algebra, variables, combining variables
```trilower(a) returns a matrix d of the same size and shape as a with
d[i,j] = a[i,j] for i >= j (on or below the diagonal) and d[i,j] = 0 for
i < j (above the diagonal).  Variable a must be a matrix but need not be
square.
[1   5   9]                   [1   0   0]
For example, when a is  [2   6  10] , trilower(a) is  [2   6   0] .
[3   7  11]                   [3   7  11]
[4   8  12]                   [4   8  12]

When a has type CHARACTER, elements above the diagonal are sent to empty

trilower(a,T) or trilower(a,pack:T) returns the lower triangle (elements
a[i,j] with i >= j) of a in packed form.  Matrix a must be square, that
is, nrows(a) = ncols(b).  For example, when
[1   4   7]
a =  [2   5   8]  ,
[3   6   9]
trilower(a) is vector(1, 2, 5, 3, 6, 9).

Note: keyword 'square' is not valid for trilower().