# Iden

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iden | |

Computes a sparse or full identity matrix | |

Other toolboxes required | none |
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Function category | Helper functions |

This is a helper function that only exists to aid other functions in QETLAB. If you are an end-user of QETLAB, you likely will never have a reason to use this function. |

` iden` is a function that computes the identity matrix of the desired size, which is either full or sparse.

## Syntax

`ID = iden(DIM,SP)`

## Argument descriptions

`DIM`: The number of rows (or equivalently, columns) that`ID`will have.`SP`: A flag (either 1 or 0) indicating whether`ID`should or should not be sparse.

## Examples

Full and sparse versions of the 2-by-2 identity matrix:

```
>> iden(2,0)
ans =
1 0
0 1
>> iden(2,1)
ans =
(1,1) 1
(2,2) 1
```

## Notes

This function is only meant to simplify code within other functions. If you always want either the full or the sparse identity matrix, just use MATLAB's built-in eye or speye function.

## Source code

Click here to view this function's source code on github.