R: Extract Lower Triangular Elements from a Symmetric Matrix

vech {MCMCpack} | R Documentation

## Extract Lower Triangular Elements from a Symmetric Matrix

### Description

This function takes a symmetric matrix and extracts a list of all lower triangular elements.

### Usage

    vech(x)

### Arguments

`x` | A symmetric matrix.

### Details

This function checks to make sure the matrix is square, but it does not check for symmetry (it just pulls the lower triangular elements). The elements are stored in column major order. The original matrix can be restored using the `xpnd` command.

### Value

A list of the lower triangular elements.

### See Also

`xpnd`

### Examples

       symmat <- matrix(c(1,2,3,4,2,4,5,6,3,5,7,8,4,6,8,9),4,4)
       vech(symmat)

[Package MCMCpack version 1.5-0 Index]