# LowerTriangularize

gives a matrix in which all but the lower triangular elements of m are replaced with zeros.

LowerTriangularize[m,k]

replaces with zeros only the elements above the k subdiagonal of m.

# Details • works even if m is not a square matrix.
• In LowerTriangularize[m,k], positive k refers to subdiagonals above the main diagonal and negative k refers to subdiagonals below the main diagonal.
• LowerTriangularize works with SparseArray objects.

# Examples

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## Basic Examples(2)

Get the lower triangular part of a matrix:

Get the strictly lower triangular part of a matrix:

## Scope(12)

### Basic Uses(8)

Get the lower triangular part of nonsquare matrices:

Find the lower triangular part of a machine-precision matrix:

Lower triangular part of a complex matrix:

Lower triangular part of an exact matrix:

Lower triangular part of an arbitrary-precision matrix:

Compute the lower triangular part of a symbolic matrix:

Large matrices are handled efficiently:

The number of rows or columns limits the meaningful values of the parameter k:

### Special Matrices(4)

The lower triangular part of a sparse matrix is returned as a sparse matrix:

Format the result:

The lower triangular part of structured matrices:

The lower triangular part of an identity matrix is the matrix itself:

This is true of any diagonal matrix:

Compute the the lower triangular part, including the superdiagonal, for HilbertMatrix:

## Properties & Relations(2)

Matrices returned by LowerTriangularize satisfy LowerTriangularMatrixQ:

LowerTriangularize[m,k] is equivalent to Transpose[UpperTriangularize[Transpose[m], -k]]: