# lowmat, lowmat1¶

## Purpose¶

Returns the lower portion of a matrix. lowmat() returns the main diagonal and every element below. lowmat1() is the same except it replaces the main diagonal with ones.

## Format¶

L = lowmat(x)
L = lowmat1(x)
Parameters

x (NxN matrix) – data

Returns

L (NxN matrix) – containing the lower elements of the matrix. The upper elements are replaced with zeros. lowmat() returns the main diagonal intact. lowmat1() replaces the main diagonal with ones.

## Examples¶

x = { 1 2 -1,
2 3 -2,
1 -2 4 };

L = lowmat(x);
L1 = lowmat1(x);


The resulting matrices are

    1  0  0       1   0   0
L = 2  3  0  L1 = 2   1   0
1 -2  4       1  -2   1


## Remarks¶

The lowmat() function along with upmat1() can be used to extract the LU factors from the return.

diag.src