Description Usage Arguments Details Value References See Also Examples

This function provides the minimum information required to create the commutation matrix.

The commutation matrix is a square matrix of order *mn* that, for an *m\times n*
matrix *\bold{A}*, transform `vec`

*(\bold{A}*) to `vec`

*(\bold{A}^T)*.

1 |

`m` |
a positive integer row dimension. |

`n` |
a positive integer column dimension. |

`condensed` |
logical. Information should be returned in compact form? |

This function returns a list containing two vectors that represent an element of
the commutation matrix and is accesed by the indexes in vectors `row`

and `col`

.
This information is used by function `comm.prod`

to do some operations
involving the commutation matrix without forming it. This information also can be
obtained using function `commutation`

.

A list containing the following elements:

`row` |
vector of indexes, each entry represents the row index of the commutation matrix. |

`col` |
vector of indexes, each entry represents the column index of the commutation
matrix. Only present if |

`m` |
positive integer, row dimension. |

`n` |
positive integer, column dimension. |

Magnus, J.R., Neudecker, H. (1979).
The commutation matrix: some properties and applications.
*The Annals of Statistics* **7**, 381-394.

1 2 3 4 5 | ```
z <- comm.info(m = 3, n = 2, condensed = FALSE)
z # where are the ones in commutation matrix of order '3,2'?
K32 <- commutation(m = 3, n = 2, matrix = TRUE)
K32 # only recommended if m and n are very small
``` |

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