eye identity matrix

## Syntax

    X = eye(m,n)
                X = eye(A)
                X = eye()

## Arguments

A,X

  matrices, hypermatrices, or `syslin` lists

m,n

  integer values: numbers of rows and columns for `X`

## Description

according to its arguments defines an `m`x`n` matrix with 1 along the main diagonal or an identity matrix of the same dimension as `A` . In case `A` is an hypermatrix, `X` will be defined as `X(i,i,...,i) = 1` for all `i` from 1 to `min(size(A))`.

`eye(10)` is interpreted as `eye(A)` with `A=10` i.e. `1`. (It is NOT a ten by ten identity matrix!).

If `A` is a linear system represented by a `syslin` list, `eye(A)` returns an `eye` matrix of appropriate dimension: (number of outputs x number of inputs).

`eye()` produces a identity matrix with undefined dimensions. Dimensions will be defined when this identity matrix is added to a matrix with fixed dimensions.

## Examples

    eye(2,3)
    A=rand(2,3);eye(A)
    s=poly(0,'s');A=[s,1;s,s+1];eye(A)
    A=[1/s,1;s,2];eye(A);
    A=ssrand(2,2,3);eye(A)
    [1 2;3 4]+2*eye()
    eye(zeros(4,4,4,4))

## See also

- ones
- zeros

## History

5.5.0

Generalization to N-D hypermatrix