# freqsepOptions

Options for slow-fast decomposition

## Syntax

``opt = freqsepOptions``
``opt = freqsepOptions(Name,Value)``

## Description

````opt = freqsepOptions` returns the default options for `freqsep`.```

example

````opt = freqsepOptions(Name,Value)` returns an options set with the options specified by one or more `Name,Value` pair arguments.```

## Examples

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Decompose a model into slow and fast components between poles that are closely spaced.

The following system includes a real pole and a complex pair of poles that are all close to s = -2.

`G = zpk(-.5,[-1.9999 -2+1e-4i -2-1e-4i],10);`

Try to decompose the model about 2 rad/s, so that the slow component contains the real pole and the fast component contains the complex pair.

`[Gs,Gf] = freqsep(G,2);`
```Warning: One or more fast modes could not be separated from the slow modes. To force separation, relax the accuracy constraint by increasing the "SepTol" factor (see "freqsepOptions" for details). ```

These poles are too close together for `freqsep` to separate. Increase the relative tolerance to allow the separation.

```options = freqsepOptions('SepTol',5e10); [Gs,Gf] = freqsep(G,2,options);```

Now `freqsep` successfully separates the dynamics.

`slowpole = pole(Gs)`
```slowpole = -1.9999 ```
`fastpole = pole(Gf)`
```fastpole = 2×1 complex -2.0000 + 0.0001i -2.0000 - 0.0001i ```

## Input Arguments

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### Name-Value Pair Arguments

Specify optional comma-separated pairs of `Name,Value` arguments. `Name` is the argument name and `Value` is the corresponding value. `Name` must appear inside quotes. You can specify several name and value pair arguments in any order as `Name1,Value1,...,NameN,ValueN`.

Example: `'SepTol',5`

Accuracy loss factor for slow-fast decomposition, specified as a nonnegative scalar value. `freqresp` ensures that the frequency responses of the original system, `G`, and the sum of the decomposed systems `G1+G2`, differ by no more than `SepTol` times the absolute accuracy of the computed value of `G(s)`. Increasing `SepTol` helps separate modes straddling the slow/fast boundary at the expense of accuracy.

## Output Arguments

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Options for `freqsep`, returned as a `freqsepOptions` options set. Use `opt` as the last argument to `freqsep` when computing slow-fast decomposition.