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dsp.DynamicFilterVisualizer

Display time-varying magnitude and phase response of digital filters

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Description

The dsp.DynamicFilterVisualizer object displays the magnitude response and phase response of time-varying digital filters or time-varying filter coefficients. The input to this object can be a filter coefficients vector or a filter System object™.

Using the dynamic filter visualizer, you can configure the plot settings, find the peak values, enable cursor measurements, and even generate script to recreate the plot with the current settings from the visualizer interface. For details, see Configure Filter Visualizer.

Creation

Syntax

dfv = dsp.DynamicFilterVisualizer
dfv = dsp.DynamicFilterVisualizer(nfft)
dfv = dsp.DynamicFilterVisualizer(nfft,Fs)
dfv = dsp.DynamicFilterVisualizer(nfft,Fs,range)
dfv = dsp.DynamicFilterVisualizer(Name=Value)

Description

dfv = dsp.DynamicFilterVisualizer returns a dynamic filter visualizer object, dfv, that displays the magnitude response of digital filters or filter coefficients.

example

dfv = dsp.DynamicFilterVisualizer(nfft) returns a dynamic filter visualizer with the FFTLength property set to nfft.

dfv = dsp.DynamicFilterVisualizer(nfft,Fs) returns a dynamic filter visualizer with the FFTLength property set to nfft and the SampleRate property set to Fs.

dfv = dsp.DynamicFilterVisualizer(nfft,Fs,range) returns a dynamic filter visualizer with the FFTLength property set to nfft, the SampleRate property set to Fs, and the FrequencyRange property set to range.

dfv = dsp.DynamicFilterVisualizer(Name=Value) returns a dynamic filter visualizer with each specified property set to the specified value. Unspecified properties have default values. You can use this syntax with any of the previous syntaxes.

example

Properties

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Frequently Used

FFT length that the dynamic filter visualizer uses to compute spectral estimates, specified as a positive integer.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set FFT Length to a positive integer.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Since R2023a

Flag to display normalized frequency, specified as one of these values:

  • true –– The filter visualizer displays the frequency response in normalized frequency units (0 to 1).

  • false –– The filter visualizer displays the frequency response in Hz. You can specify the input sample rate through the SampleRate property.

Scope Window Use

On the Scope tab, click Settings, and select Normalized Frequency.

Data Types: logical

Sampling rate of the input signal, specified as a real positive scalar in Hz.

Tunable: Yes

Dependency

To enable this property, set NormalizedFrequency to false. (since R2023a)

Scope Window Use

On the Scope tab, click Settings, and set Sample Rate (Hz) to a positive scalar.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Range of the frequency axis, specified as a two-element numeric vector that is monotonically increasing and of the form [fmin, fmax].

  • When you set the NormalizedFrequency property to true, fmax is in normalized frequency units and must be a positive scalar that is less than or equal to 1. (since R2023a)

  • When you set the NormalizedFrequency property to false, fmax is in Hz and must be less than or equal to Fs/2, where Fs is the value you specify in the SampleRate property. (since R2023a)

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set Range to a two-element numeric vector.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

X-axis scale, specified as either 'Linear' or 'Log'.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set X-Scale.

Y-axis units, specified as one of the following:

  • 'Magnitude'

  • 'Magnitude (dB)'

  • 'Magnitude squared'

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set Display Unit.

  • true – The filter visualizer plots the magnitude and phase responses of the filter on two separate axes.

  • false – The filter visualizer plots only the magnitude response of the filter.

Tunable: Yes

Scope Window Use

On the Scope tab, click the Magnitude Phase button.

Specify the type of plot to use in the filter visualizer window as one of these:

  • "Line" – The filter visualizer connects each point on the magnitude and phase response plot with a line.

  • "Stairs" – The filter visualizer displays the filter response (magnitude, phase, or both) as a stair-step graph. A stair-step graph is made up of only horizontal lines and vertical lines. Each horizontal line represents the filter response over a frequency value and is connected to two vertical lines. Each vertical line represents a change in values occurring at a frequency.

  • "Stem" – The filter visualizer displays the frequency response as circles with vertical lines extending down to the x-axis at each of the frequency values.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set Plot Type.

Specify the scaling mode for the axes as one of these:

  • "Auto" — The filter visualizer scales the axes as needed to fit the data, both during and after simulation.

  • "Manual" — The filter visualizer does not scale the axes automatically.

  • "OnceAtStop" — The filter visualizer scales the axes when the simulation stops.

  • "Updates" — The filter visualizer scales the axes limits once after a set number of visual updates. The number of updates is determined by the value of the AxesScalingNumUpdates property.

Tunable: Yes

Scope Window Use

Hover over the filter visualizer to see the maximize Maximize button, pan Panning icon, zoom Zoom icon, and autoscale autoscale icon buttons. You can also zoom and pan using your mouse.

Data Types: char | string

Specify the number of updates before scaling as a real, positive scalar integer.

Tunable: Yes

Dependency

To enable this property, set AxesScaling to "Updates".

Data Types: double

Measurements

Channel for which to obtain measurements, specified as a positive integer in the range [1 N], where N is the number of input channels.

Tunable: Yes

Scope Window Use

Click the Measurements tab on the Dynamic Filter Visualizer toolstrip. In the Channel section, select a Channel.

Data Types: double

Cursor measurements to display waveform cursors, specified as a CursorMeasurementsConfiguration object.

All CursorMeasurementsConfiguration properties are tunable.

Tunable: Yes

Scope Window Use

Click the Measurements tab on the Dynamic Filter Visualizer toolstrip and modify the cursor measurements in the Cursors section.

Peak finder measurements to compute and display the largest calculated peak values, specified as a PeakFinderConfiguration object.

All PeakFinderConfiguration properties are tunable.

Tunable: Yes

Scope Window Use

Click the Measurements tab on the Dynamic Filter Visualizer toolstrip and modify the peak finder measurements in the Peaks section.

Visualization

Caption to display on the Dynamic Filter Visualizer window, specified as a character vector or a string scalar.

Example: 'Dynamic Filter Visualizer'

Example: "Dynamic Filter Visualizer"

Tunable: Yes

Scope window position in pixels, specified as a four-element double vector of the form [left bottom width height]. The default value of this property is dependent on the screen resolution, and is such that the window is positioned in the center of the screen, with a width and height of 800 and 500 pixels, respectively.

Tunable: Yes

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Specify whether to display the filter visualizer in maximized-axes mode. In this mode, the axes are expanded to fit into the entire display. To conserve space, labels do not appear in each display. Instead, tick-mark values appear on top of the plotted data. You can select one of the following options:

  • "Auto" — The axes appear maximized in all displays only if the Title and YLabel properties are empty for every display. If you enter any value in any display for either of these properties, the axes are not maximized.

  • "On" — The axes appear maximized in all displays. Any values entered into the Title and YLabel properties are hidden.

  • "Off" — None of the axes appear maximized.

Tunable: Yes

Scope Window Use

Hover over the Dynamic Filter Visualizer window to see the maximize axes button .

Data Types: char | string

Display title, specified as a character vector or a string scalar.

Example: 'Magnitude Response'

Example: "Magnitude Response"

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set Title to a character vector or a string scalar.

Y-axis limits, specified as a two-element numeric row vector with the second element greater than the first element and of the form [ymin, ymax].

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set Y-Limits to a two-element numeric vector.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

When this property is set to false, no legend is displayed. When this property is set to true, a legend with automatic string labels for each input filter is displayed.

Tunable: Yes

Scope Window Use

On the Scope tab, click Legend.

Data Types: logical

Names to label the input filters in the legend, specified as a cell array of character vectors or an array of strings. The default is an empty cell array. When this property is set to an empty cell array, the filters are named by default names, such as Filter 1, Filter 2, and so on.

Tunable: Yes

Scope Window Use

On the Scope tab, click Legend. In the legend that appears on the plot, click the filter name.

Set this property to true to show grid lines on the plot.

Scope Window Use

On the Scope tab, click Settings, and select Show Grid.

Upper limit spectral mask, specified as a two-column matrix. The first column represents the frequency values (Hz), and the second column represents the magnitude spectrum of the upper limit mask.

Tunable: Yes

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Lower limit spectral mask, specified as a two-column matrix. The first column represents the frequency values (Hz), and the second column represents the magnitude spectrum of the lower limit mask.

Tunable: Yes

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Color and Styling

Since R2024b

Background color in scope, specified as an RGB triplet, a hexadecimal color code, a color name, or a short name. For more information on all the acceptable values, see Color.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and select a Background color.

Data Types: double | char

Since R2024b

Color of the axes in the scope, specified as an RGB triplet, a hexadecimal color code, a color name, or a short name. For more information on all the acceptable values, see Color.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and select an Axes color.

Data Types: double | char

Since R2024b

Colors of the labels in the scope, specified as an RGB triplet, a hexadecimal color code, a color name, or a short name. Use this property to set the color of the scope title, x-axis and y-axis labels, and the axes ticks. For more information on all the acceptable values, see Color.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and select a Labels color.

Data Types: double | char

Since R2024b

Scope font size, specified as a positive scalar. Use this property to set the font size for the ticks, labels, title, and measurements of the scope.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set the Font Size to one of the available values.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Since R2024b

Visibility of plot lines in scope, specified as one of these:

  • "on" or 1 –– The scope displays the plot line. If you are plotting multiple lines, the scope applies this value to all the lines.

  • "off" or 0 –– The scope hides the plot line. If you are plotting multiple lines, the scope applies this value to all the lines.

  • vector of logical values –– The scope applies the values to the lines in the plot. The length of the vector must equal the number of lines that you are plotting in the scope.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and select the Visible property.

Data Types: logical

Since R2024b

Scope line style, specified as one of these options:

  • "-" –– Solid line

  • "--" –– Dashed line

  • ":" –– Dotted line

  • "-." –– Dash-dotted line

  • "none" –– No line

If you provide a cell array or an array of these values, then the length of the array must equal the number of lines that you are plotting in the scope.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set Style.

Since R2024b

Scope line width, specified as a positive scalar or a vector of positive scalar values in points, where 1 point = 1/72 of an inch. If you specify a scalar value and are plotting multiple lines, then the scope applies the same value to all the lines. If you provide a vector of values, the length of the vector must equal the number of lines that you are plotting.

If the line has markers, then the line width also affects the marker edges. The line width cannot be thinner than the width of a pixel. If you set the line width to a value that is less than the width of a pixel on your system, the line displays as one pixel wide.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set Width.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Since R2024b

Scope line color, specified as a matrix of RGB triplets or an array of color names.

Tunable: Yes

Matrix of RGB Triplets

Specify an m-by-3 matrix, where each row is an RGB triplet. An RGB triplet is a three-element vector containing the intensities of the red, green, and blue components of a color. The intensities must be in the range [0,1]. For example, this matrix defines the new colors as blue, dark green, and orange.

scope.LineColor = [1.0 0.0 0.0
                0.0 0.4 0.0
                1.0 0.5 0.0];

Array of Color Names or Hexadecimal Color Codes

Specify any combination of color names, short names, or hexadecimal color codes.

  • To specify one color, set the line color to a character vector or a string scalar. For example, scope.LineColor = 'red' specifies red as the only color in the color order.

  • To specify multiple colors, set LineColor to a cell array of character vectors or a string array. For example, scope.LineColor = {'red','green','blue'} specifies red, green, and blue as the colors.

A hexadecimal color code starts with a hash symbol (#) followed by three or six hexadecimal digits, which can range from 0 to F. The values are not case sensitive. Thus, the color codes '#FF8800', '#ff8800', '#F80', and '#f80' are equivalent.

This table lists the color names and short names with the equivalent RGB triplets and hexadecimal color codes.

Color NameShort NameRGB TripletHexadecimal Color CodeAppearance
"red""r"[1 0 0]"#FF0000"

Sample of the color red

"green""g"[0 1 0]"#00FF00"

Sample of the color green

"blue""b"[0 0 1]"#0000FF"

Sample of the color blue

"cyan" "c"[0 1 1]"#00FFFF"

Sample of the color cyan

"magenta""m"[1 0 1]"#FF00FF"

Sample of the color magenta

"yellow""y"[1 1 0]"#FFFF00"

Sample of the color yellow

"black""k"[0 0 0]"#000000"

Sample of the color black

"white""w"[1 1 1]"#FFFFFF"

Sample of the color white

Scope Window Use

On the Scope tab, click Settings, and set Color.

Data Types: single | double | char | string | cell

Since R2024b

Scope line marker symbol, specified as one of the values listed in this table. By default, the object does not display markers. Specifying a marker symbol adds markers at each data point or vertex.

Tunable: Yes

Scope Window Use

On the Scope tab, click Settings, and set Marker.

Usage

Syntax

dfv(filt)
dfv(B,A)

Description

dfv(filt) displays the time-varying magnitude response of the object filter, filt, in the Dynamic Filter Visualizer figure, as long as filt has a valid freqz() implementation.

dfv(B,A) displays the magnitude response for the digital filters with numerator and denominator polynomial coefficients stored in B1 and A1, B2 and A2, ..., and BN and AN, respectively.

Input Arguments

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Input filter System object with a valid freqz() implementation.

Numerator polynomial coefficients, specified as a row vector.

Data Types: single | double

Denominator polynomial coefficients, specified as a:

  • scalar –– The filter is an FIR filter.

  • row vector –– The filter is an IIR filter.

Data Types: single | double

Object Functions

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stepDisplay time-varying magnitude response
printToFigurePrint scope window to MATLAB figure
showDisplay scope window
hideHide scope window
isVisibleDetermine visibility of scope
generateScriptGenerate MATLAB script to create scope with current settings

Examples

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Open Live Script

Design an FIR filter with a time-varying magnitude and phase response. Plot this varying response on a dynamic filter visualizer in normalized frequency units.

Create a dsp.DynamicFilterVisualizer object. Set the PlotAsMagnitudePhase and the NormalizedFrequency properties to true.

dfv = dsp.DynamicFilterVisualizer(PlotAsMagnitudePhase=1,...
    NormalizedFrequency=true,ShowLegend=true,...
    Title='Magnitude and Phase Response',...
    FilterNames="FIR Filter")
dfv = 
  dsp.DynamicFilterVisualizer handle with properties:

               FFTLength: 2048
     NormalizedFrequency: 1
          FrequencyRange: [0 1]
                  XScale: 'Linear'
        MagnitudeDisplay: 'Magnitude (dB)'
    PlotAsMagnitudePhase: 1
                PlotType: 'Line'
             AxesScaling: 'Auto'

  Show all properties

Vary the cutoff frequency of the FIR filter k from 0.1 to 0.5 in increments of 0.001. View the varying magnitude and phase response using the dynamic filter visualizer.

for k = 0.1:0.001:0.5
    b = designLowpassFIR(FilterOrder=90,CutoffFrequency=k);
    dfv(b,1);
end

Open Live Script

Visualize the varying magnitude response of the variable bandwidth FIR filter using the dynamic filter visualizer.

Create a dsp.DynamicFilterVisualizer object.

dfv = dsp.DynamicFilterVisualizer(YLimits=[-160 10],...
    FilterNames="Variable Bandwidth FIR Filter")
dfv = 
  dsp.DynamicFilterVisualizer handle with properties:

               FFTLength: 2048
     NormalizedFrequency: 0
              SampleRate: 44100
          FrequencyRange: [0 22050]
                  XScale: 'Linear'
        MagnitudeDisplay: 'Magnitude (dB)'
    PlotAsMagnitudePhase: 0
                PlotType: 'Line'
             AxesScaling: 'Manual'

  Show all properties

Design a bandpass variable bandwidth FIR filter with a center frequency of 5 kHz and a bandwidth of 4 kHz.

Fs = 44100;
vbw = dsp.VariableBandwidthFIRFilter(FilterType='Bandpass',...
    FilterOrder=100,...
    SampleRate=Fs,...
    CenterFrequency=5e3,...
    Bandwidth=4e3);

Vary the center frequency of the filter. Visualize the varying magnitude response of the filter using the dsp.DynamicFilterVisualizer object.

for idx  = 1:100
    dfv(vbw);
    vbw.CenterFrequency = vbw.CenterFrequency + 20;
end

Since R2024b

Open Live Script

Create a dsp.DynamicFilterVisualizer object and set the NormalizedFrequency property to true. Create three bandpass FIR filters with varying center frequencies. 

filtViz = dsp.DynamicFilterVisualizer(NormalizedFrequency=true);
filt1 = designBandpassFIR(FilterOrder=100,CenterFrequency=0.3,...
    Bandwidth=0.1,SystemObject=true);
filt2 = designBandpassFIR(FilterOrder=100,CenterFrequency=0.4,...
    Bandwidth=0.1,SystemObject=true);
filt3 = designBandpassFIR(FilterOrder=100,CenterFrequency=0.5,...
    Bandwidth=0.1,SystemObject=true);

Visualize the filters in the filter visualizer. This plot shows the default color and style settings of the object.

filtViz(filt1,filt2,filt3)
release(filtViz);

Change the background color and the axes color of the plot to "white". Set the font color to "black". Also, change the line colors to ["red" "green" "black"].

filtViz.BackgroundColor = "white";
filtViz.AxesColor = "white";
filtViz.FontColor = "black";
filtViz.LineColor = ["red" "green" "black"];
show(filtViz)
release(filtViz)

To change the color order, set LineColor to a different color order. This setting changes the color order palette.

filtViz.LineColor = colororder("glow");
show(filtViz)
release(filtViz)

To control the visibility of the plot lines, use the LineVisible property. When you select "off", the plot line becomes invisible.

filtViz.LineVisible = ["off" "on" "on"];
show(filtViz)
release(filtViz)

You can further specify a marker for each line and change the corresponding line width.

filtViz.LineMarker = ["x","o","+"];
filtViz.LineWidth = 2;
show(filtViz)
release(filtViz)

Since R2023b

Open Live Script

Use the printToFigure function to print the dsp.DynamicFilterVisualizer object display window to a new MATLAB® figure.

Create a dsp.DynamicFilterVisualizer object.

dfv = dsp.DynamicFilterVisualizer(YLimits=[-120 10]);

Design FIR filter with varying cutoff frequencies ranging from 0.1 to 0.5. Plot the magnitude response of the filter using the Dynamic Filter Visualizer.

for k = 0.1:0.001:0.5
    b = fir1(90, k);
    dfv(b,1);
end

Change the background color and the axes color of the plot to "white". Set the font color to "black" and the line color to "blue".

dfv.BackgroundColor = "white";
dfv.AxesColor = "white";
dfv.FontColor = "black";
dfv.LineColor = "blue";
show(dfv)
release(dfv)

Print the display of the magnitude response to a new MATLAB figure. The function returns a handle to the figure.

scopeFig = printToFigure(dfv);

Figure contains an axes object. The axes object contains an object of type image.

The handle to the figure scopeFig lets you modify the appearance and the behavior of the figure window.

Specify a figure name and change the size of the figure to 400-by-250 pixels.

scopeFig.Name="Magnitude Response of FIR Filter";
scopeFig.NumberTitle="off";
scopeFig.Position=[1 1 400 250];

Figure Magnitude Response of FIR Filter contains an axes object. The axes object contains an object of type image.

When printing to figure, you can make the figure invisible by setting the Visible argument to false.

scopeFig = printToFigure(dfv,Visible=false);

Limitations

  • Does not support C/C++ code generation using MATLAB® Coder™. To generate a standalone application, use the MATLAB Compiler™.

  • Supports MEX code generation by treating the calls to the object as extrinsic.

Version History

Introduced in R2018b

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See Also

Functions

Objects

Blocks

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