# Manuals/calci/ARROWHEAD

**MATRIX("ARROWHEAD",order)**

- is the order of the arrowhead matrix.

## Description

- This function returns the matrix with the type arrowhead.
- In mathematical, a square matrix containing zeros in all entries except for the first row first column and main diagonal.
- i.e., The matrix of the form

A=

- So Calci displays, the elements of the arrowhead matirx are 1 except 1st row and column and main diagonal.
- The matrix has the form Any symmetric permutation of the arrowhead matrix, where P is a permutation matrix is a arrowhead matrix.
- i.e., where P is a permutation matrix is a arrowhead matrix.
- Real symmetric arrowhead matrices are often an essential tool for the computation of the eigenvalues

## Examples

- MATRIX("arrowhead") = 1
- MATRIX("arrowhead",3)

1 | 1 | 1 |

1 | 1 | 0 |

1 | 0 | 1 |

- MATRIX("arrowhead",5)

1 | 1 | 1 | 1 | 1 |

1 | 1 | 0 | 0 | 0 |

1 | 0 | 1 | 0 | 0 |

1 | 0 | 0 | 1 | 0 |

1 | 0 | 0 | 0 | 1 |