spectrumplot

Plot disturbance spectrum of linear identified models

Syntax

``spectrumplot(sys)``
``spectrumplot(sys,line_spec)``
``spectrumplot(sys1,line_spec1,...,sysN,line_specN)``
``spectrumplot(ax,___)``
``spectrumplot(___,plot_options)``
``spectrumplot(sys,{wmin,wmax})``
``spectrumplot(sys,w)``
``h = spectrumplot()``

Description

example

````spectrumplot(sys)` plots the disturbance spectrum of the model, `sys`. The software chooses the number of points on the plot and the plot frequency range.```

example

````spectrumplot(sys,line_spec)` uses `line_spec` to specify the line type, marker symbol, and color.```

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````spectrumplot(sys1,line_spec1,...,sysN,line_specN)` plots the disturbance spectrum for one or more models on the same axes.You can mix `sys`, `line_spec` pairs with `sys` models as in `spectrumplot(sys1,sys2,line_spec2,sys3)`. `spectrumplot` automatically chooses colors and line styles in the order specified by the `ColorOrder` and `LineStyleOrder` properties of the current axes.```

example

````spectrumplot(ax,___)` plots into the axes with handle `ax`. All input arguments described for the previous syntaxes also apply here.```

example

````spectrumplot(___,plot_options)` uses plot_options to specify options such as plot title, frequency units, etc. All input arguments described for the previous syntaxes also apply here.```

example

````spectrumplot(sys,{wmin,wmax})` creates a spectrum plot for frequencies ranging from `wmin` to `wmax`.```

example

````spectrumplot(sys,w)` uses vector `w` to specify the plot frequencies.```

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````h = spectrumplot()` returns the handle to the spectrum plot. You use the handle to customize the plot. All input arguments described for the previous syntaxes also apply here.```

Examples

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Obtain the identified model.

```load iddata9 z9 sys = ar(z9,4);```

Plot the output spectrum for the model.

`spectrumplot(sys);`

Obtain the identified model.

```load iddata9 z9 sys = ar(z9,4);```

Specify the line width and marker style for the spectrum plot.

`spectrumplot(sys,'k*--');`

`'k*--'`, specifies a dashed line (`--`) that is black (`k`), with star markers (`*`).

Obtain multiple identified models.

```load iddata9 z9 sys1 = ar(z9,4); sys2 = ar(z9,2);```

Plot the output spectrum for both models.

```spectrumplot(sys1,'b*-',sys2,'g^:'); legend('sys1','sys2');```

Obtain the axes handle for a plot.

```load iddata9 z9 sys1 = ar(z9,4); spectrumplot(sys1);```

`ax = gca;`

`ax` is the handle for the spectrum plot axes.

Plot the output spectrum for another model on the specified axes.

```sys2 = ar(z9,2); hold on; spectrumplot(ax,sys2,'r*--'); legend('sys1','sys2');```

Specify the plot options.

```plot_options = spectrumoptions; plot_options.FreqUnits = 'Hz'; plot_options.FreqScale = 'linear'; plot_options.Xlim = {[0 20]}; plot_options.MagUnits = 'abs';```

Estimate an `AR` model.

```load iddata9 z9 sys = ar(z9,4);```

Plot the output spectrum for the model.

`spectrumplot(sys,plot_options);`

Obtain the identified model.

```load iddata9 z9 sys = ar(z9,4);```

Specify the frequency range for the output spectrum plot for the model.

`spectrumplot(sys,{1,1000});`

The 2-element cell array `{1,1000}` specifies the frequency range from 1 rad/s to 1000 rad/s.

```w = [1:100:1000]; spectrumplot(sys, w);```

The numeric vector `w` specifies the frequency range from 1 rad/s to 1000 rad/s updating the plot every 100 data points.

Obtain the identified model.

```load iddata9 z9 sys = ar(z9,4);```

Get the plot handle for the model spectrum plot.

`h = spectrumplot(sys);`

(Optional) Specify the plot options, using the plot handle.

`setoptions(h,'FreqUnits','Hz','FreqScale','linear','Xlim',{[0 20]},'MagUnits','abs');`

Input Arguments

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Identified linear model, specified as an `idpoly` object, an `idproc` object, an `idss` object, or an `idtf` object.

Line style, marker, and color of both the line and marker, specified as a character vector or string. The characters can appear in any order. You do not need to specify all three characteristics (line style, marker, and color). For example, `'b'`, `'b+:'`. See the `LineSpec` argument of the `plot` function.

Example: `"blue"` specifies a blue solid line

Example: `"r*:"` specifies a red dotted line with asterisk markers

Example: `"y"` specifies a yellow solid line

Data Types: `char` | `string`

Plot axes handle for a spectrum plot, returned as a double-precision value.

You can obtain the current axes handle by using the function, `gca`.

Minimum frequency of the frequency range for which to plot the spectrum, specified as a positive number. Specify `wmin` in `rad/TimeUnit`, where `TimeUnit` is `sys.TimeUnit`.

For an example of specifying `wmin`, see Specify Spectrum Plot Frequency Range.

Maximum frequency of the frequency range for which to plot the spectrum, specified as a positive number. Specify `wmax` in `rad/TimeUnit`, where `TimeUnit` is `sys.TimeUnit`.

For an example of specifying `wmin`, see Specify Spectrum Plot Frequency Range.

Frequencies for which to plot the spectrum, specified as a vector of positive numbers.

Specify `w` in `rad/TimeUnit`, where `TimeUnit` is `sys.TimeUnit`.

You can use the command, `spectrumoptions`, to create the `plot_options` object. For more information, see `spectrumoptions`.

Output Arguments

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The plot handle for the generated spectrum plot, returned as a double-precision value.

Version History

Introduced in R2012b