# UNIT matrix function

## Description

UNIT(**A**) returns a unit matrix (identity matrix) with the same dimensions of the square matrix **A**.

UNIT(*n*) returns a square unit or identity *n* × *n* matrix.

The square n × n identity matrix, denoted *I _{n}*, is a matrix with 1's on the diagonal and 0's elsewhere.

When matrix *A* is

$$ A=\begin{bmatrix}

5&2 \\

2&7

\end{bmatrix} $$

5&2 \\

2&7

\end{bmatrix} $$

then

$$ UNIT(A)=\begin{bmatrix}

1&0\\

0&1

\end{bmatrix} $$

1&0\\

0&1

\end{bmatrix} $$

In multiplication, an identity element is a neutral element. The identity matrix plays the same role as the number 1 in ordinary arithmetic:

$$ \begin{bmatrix}

5&2 \\

2&7

\end{bmatrix} \begin{bmatrix}

1&0\\

0&1

\end{bmatrix} = \begin{bmatrix}

5&2 \\

2&7

\end{bmatrix} $$

5&2 \\

2&7

\end{bmatrix} \begin{bmatrix}

1&0\\

0&1

\end{bmatrix} = \begin{bmatrix}

5&2 \\

2&7

\end{bmatrix} $$

## Calculator

## See also

## Recommended book

## Matrix Algebra Useful for Statistics

Shayle R. Searle, Andre I. Khuri

Buy from Amazon

This book addresses matrix algebra that is useful in the statistical analysis of data as well as within statistics as a whole. The material is presented in an explanatory style rather than a formal theorem-proof format and is self-contained.