Description

The ArrayPlot object displays vectors or arrays.

To display vectors or array in Array Plot:

1. Define and set up your Array Plot. See Construction.

2. Call step to display the vectors or arrays in the Array Plot figure. The behavior of step is specific to each object in the toolbox.

Use the MATLAB^® clear function to close the Array Plot figure window and clear its associated data. Use the hide method to hide the ArrayPlot window and the show method to make it visible.

Use the MATLAB mcc function to compile code containing an Array Plot.

See the following sections for more information on the Array Plot Graphical User Interface:

• Signal Display

• Toolbar

• Measurements Panels

• Visuals — Array Plot Properties

• Style Dialog Box

• Tools — Plot Navigation Properties

Note:   Starting in R2016b, instead of using the step method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

Construction

H = dsp.ArrayPlot creates an Array Plot System object, H. This object displays vectors or arrays.

H = dsp.ArrayPlot('Name',Value,...) creates an Array Plot System object, H, with each specified property Name set to the specified value. You can specify Name–Value arguments in any order.

Properties

Methods

Examples

The following examples illustrate how to use the Array Plot object to view a variety of input signals.

Plot a Gaussian Distribution

Note: This example runs only in R2016b or later. If you are using an earlier release, replace each call to the function with the equivalent step syntax. For example, myObject(x) becomes step(myObject,x).

View a Gaussian, or normal, distribution on the Array Plot figure.

Create a new Array Plot object.

h = dsp.ArrayPlot;

Configure the properties of the Array Plot object for a Gaussian distribution.

h.YLimits = [0 1];
h.XOffset = -2.5;
h.SampleIncrement = 0.1;
h.Title = 'Gaussian distribution';
h.XLabel = 'X';
h.YLabel = 'f(X)';

Call the dsp.ArrayPlot.step method to plot a Gaussian distribution.

h(exp(-(-2.5:.1:2.5).*(-2.5:.1:2.5))');

Plot Changing Filter Weights

Note: This example runs only in R2016b or later. If you are using an earlier release, replace each call to the function with the equivalent step syntax. For example, myObject(x) becomes step(myObject,x).

View Least Mean Squares (LMS) adaptive filter weights on the Array Plot figure. Watch the filter weights change as they adapt to filter a noisy input signal.

Create an LMS adaptive filter System object.

hlms = dsp.LMSFilter(40,'Method', 'Normalized LMS', 'StepSize', .002);

Create and configure an audio file reader System object to read the input signal from the specified audio file.

hsigsource = dsp.AudioFileReader('dspafxf_8000.wav',  ...
    'SamplesPerFrame', 40, ...
    'PlayCount', Inf,...
    'OutputDataType', 'double');

Create and configure a fixed-point Finite Impulse Response (FIR) digital filter System object to filter random white noise, creating colored noise.

hfilt = dsp.FIRFilter('Numerator', fir1(39, .25));

Create and configure an Array Plot System object to display the adaptive filter weights.

harrayplot = dsp.ArrayPlot('XLabel', 'Filter Tap', ...
    'YLabel', 'Filter Weight', ...
    'YLimits', [-.05 .2]');

Plot the LMS filter weights as they adapt to a desired signal. Read from the audio file, produce random data, and filter the random data. Update the filter weights and plot the filter weights.

numplays = 0;
while numplays < 3
    [y, eof]    = hsigsource();
    noise       = rand(40,1);
    noisefilt   = hfilt(noise);
    desired     = y + noisefilt;
    [~, ~, wts] = hlms(noise, desired);
    harrayplot(wts);
    numplays = numplays + eof;
end

Signal Display

Array Plot uses the XOffset and SampleIncrement properties to determine the time range. To change the X-offset setting in the Array Plot figure, select View > Configuration Properties. The Visuals — Array Plot Properties dialog box appears. Go to the Main tab, and modify the value for the X-offset.

The span of the x-axis data is related to the SampleIncrement property by the equation $$x_{span}=\text{SampleIncrement}\times (\mathrm{length}(x)-1)$$. Suppose you set SampleIncrement to 0.1 and the input signal data has 51 samples. The scope displays values on the x-axis from 0 to 5. If you also set the X-offset to –2.5, the scope displays values on the x-axis from –2.5 to 2.5. The values on the x-axis of the scope display remain the same throughout simulation.

The following figure highlights the important aspects of the Array Plot window.

Indicators

• Minimum x-axis limit — Array Plot sets the minimum x-axis limit using the value of the X-offset parameter on the Main tab of the Visuals—Array Plot Properties dialog box.

• Maximum x-axis limit — Array Plot sets the maximum x-axis limit by summing the value of X-offset parameter with the span of x-axis values. The equation $$x_{span}=\text{SampleIncrement}\times (\mathrm{length}(x)-1)$$ defines the relationship of the span of the x-axis data to the SampleIncrement property.

• Simulation status — Provides the current status of the model simulation. The status can be either of the following conditions:

  • Processing — Occurs after you run the step method and before you run the release method.

  • Stopped — Occurs after you construct the scope object and before you first run the step method. This status also occurs after you run the release method.

  The Simulation status is part of the Status Bar in the scope window. You can choose to hide or display the entire Status Bar. From the scope menu, select View > Status Bar.

Multiple Signal Names and Colors

By default, if the input signal has multiple channels, the scope uses an index number to identify each channel of that signal. For example, a 2-channel signal would have the following default names in the channel legend: Channel 1, Channel 2. To show the legend, select View > Configuration Properties, click the Display tab, and select the Show Legend check box. If there are a total of 7 input channels, the following legend appears in the display.

By default, the scope has a black axes background and chooses line colors for each channel in a manner similar to the Simulink^® Scope block. When the scope axes background is black, it assigns each channel of each input signal a line color in the order shown in the above figure.

If there are more than 7 channels, then the scope repeats this order to assign line colors to the remaining channels. To choose line colors for each channel, change the axes background color to any color except black. To change the axes background color to white, select View > Style, click the Axes background color button ( ), and select white from the color palette. Run the simulation again. The following legend appears in the display. This is the color order when the background is not black.

Toolbar

The Array Plot toolbar contains the following buttons.

Print, Settings, and Properties Buttons

Zoom and Axes Control Buttons

Measurements Buttons

Note:   The zoom buttons do not change the settings related to span for the scope. These buttons are purely graphical.

You can control whether this toolbar appears in the Array Plot window. From the menu, select View > Toolbar.

Measurements Panels

The Measurements panels are the panels that appear to the right side of the Array Plot figure. These panels are labeled Trace selection, Cursor Measurements, Signal Statistics, and Peak Finder.

Measurements Panel Buttons

Each of the Measurements panels contains the following buttons that enable you to modify the appearance of the current panel.

Button	Description
	Move the current panel to the top. When you are displaying more than one panel, this action moves the current panel above all the other panels.
	Collapse the current panel. When you first enable a panel, by default, it displays one or more of its panes. Click this button to hide all of its panes to conserve space. After you click this button, it becomes the expand button .
	Expand the current panel. This button appears after you click the collapse button to hide the panes in the current panel. Click this button to display the panes in the current panel and show measurements again. After you click this button, it becomes the collapse button again.
	Undock the current panel. This button lets you move the current panel into a separate window that can be relocated anywhere on your screen. After you click this button, it becomes the dock button in the new window.
	Dock the current panel. This button appears only after you click the undock button. Click this button to put the current panel back into the right side of the Scope window. After you click this button, it becomes the undock button again.
	Close the current panel. This button lets you remove the current panel from the right side of the Scope window.

Some panels have their measurements separated by category into a number of panes. Click the pane expand button to show each pane that is hidden in the current panel. Click the pane collapse button to hide each pane that is shown in the current panel.

Trace Selection Panel

When you use the scope to view multiple signals, the Trace Selection panel appears if you have more than one signal displayed and you click any of the other Measurements panels. The Measurements panels display information about only the signal chosen in this panel. Choose the signal name for which you would like to display time domain measurements. See the following figure.

You can choose to hide or display the Trace Selection panel. In the Scope menu, select Tools > Measurements > Trace Selection.

Cursor Measurements Panel

The Cursor Measurements panel displays screen cursors. The panel provides two types of cursors for measuring signals. Waveform cursors are vertical cursors that track along the signal. Screen cursors are both horizontal and vertical cursors that you can place anywhere in the display.

Note:   If a data point in your signal has more than one value, the cursor measurement at that point is undefined and no cursor value is displayed.

In the Scope menu, select Tools > Measurements > Cursor Measurements. Alternatively, in the Scope toolbar, click the Cursor Measurements button.

The Cursor Measurements panel is separated into two panes, labeled Settings and Measurements. You can expand each pane to see the available options.

You can use the mouse or the left and right arrow keys to move vertical or waveform cursors and the up and down arrow keys for horizontal cursors.

 Settings Pane

 Measurements Pane

Signal Statistics Panel

The Signal Statistics panel displays the maximum, minimum, peak-to-peak difference, mean, median, and RMS values of a selected signal. It also shows the x-axis indices at which the maximum and minimum values occur. You can choose to hide or display the Signal Statistics panel. In the scope menu, select Tools > Measurements > Signal Statistics. Alternatively, in the scope toolbar, click the Signal Statistics button.

 Signal Statistics Measurements

When you use the zoom options in the scope, the Signal Statistics measurements automatically adjust to the time range shown in the display. In the scope toolbar, click the Zoom In or Zoom X button to constrict the x-axis range of the display, and the statistics shown reflect this time range. For example, you can zoom in on one pulse to make the Signal Statistics panel display information about only that particular pulse.

The Signal Statistics measurements are valid for any units of the input signal. The letter after the value associated with each measurement represents the appropriate International System of Units (SI) prefix, such as m for milli-. For example, if the input signal is measured in volts, an m next to a measurement value indicates that this value is in units of millivolts.

Peak Finder Panel

Note:   The Peak Finder panel requires a DSP System Toolbox™ or Simscape™ license.

The Peak Finder panel displays the maxima, showing the x-axis values at which they occur. Peaks are defined as a local maximum where lower values are present on both sides of a peak. Endpoints are not considered to be peaks. This panel allows you to modify the settings for peak threshold, maximum number of peaks, and peak excursion. You can choose to hide or display the Peak Finder panel. In the scope menu, select Tools > Measurements > Peak Finder. Alternatively, in the scope toolbar, select the Peak Finder button.

The Peak finder panel is separated into two panes, labeled Settings and Peaks. You can expand each pane to see the available options.

The Settings pane enables you to modify the parameters used to calculate the peak values within the displayed portion of the input signal. For more information on the algorithms this pane uses, see the Signal Processing Toolbox findpeaks function reference.

• Peak Threshold — The level above which peaks are detected. This setting is equivalent to the MINPEAKHEIGHT parameter, which you can set when you run the findpeaks function.

• Max Num of Peaks — The maximum number of peaks to show. The value you enter must be a scalar integer from 1 through 99. This setting is equivalent to the NPEAKS parameter, which you can set when you run the findpeaks function.

• Min Peaks Distance — The minimum number of samples between adjacent peaks. This setting is equivalent to the MINPEAKDISTANCE parameter, which you can set when you run the findpeaks function.

• Peak Excursion — The minimum height difference between a peak and its neighboring samples The peak excursion setting is equivalent to the THRESHOLD parameter, which you can set when you run the findpeaks function.

• Label Format — The coordinates to display next to the calculated peak values on the plot. To see peak values, expand the Peaks pane and select the check boxes associated with individual peaks of interest. By default, both x-axis and y-axis values are displayed on the plot. Select which axes values you want to display next to each peak symbol on the display.

  • X+Y — Display both x-axis and y-axis values.

  • X — Display only x-axis values.

  • Y — Display only y-axis values.

The Peaks pane displays all of the largest calculated peak values. It also shows the coordinates at which the peaks occur, using the parameters you define in the Settings pane. You set the Max Num of Peaks parameter to specify the number of peaks shown in the list.

The numerical values displayed in the Value column are equivalent to the pks output argument returned when you run the findpeaks function. The numerical values displayed in the second column are similar to the locs output argument returned when you run the findpeaks function.

The Peak Finder displays the peak values in the Peaks pane. By default, the Peak Finder panel displays the largest calculated peak values in the Peaks pane in decreasing order of peak height. Use the sort descending button ( ) to rearrange the category and order by which Peak Finder displays peak values. Click this button again to sort the peaks in ascending order instead. When you do so, the arrow changes direction to become the sort ascending button ( ). A filled sort button indicates that the peak values are currently sorted in the direction of the button arrow. If the sort button is not filled ( ), then the peak values are sorted in the opposite direction of the button arrow. The Max Num of Peaks parameter still controls the number of peaks listed.

Use the check boxes to control which peak values are shown on the display. By default, all check boxes are cleared and the Peak Finder panel hides all the peak values. To show all the peak values on the display, select the check box in the top-left corner of the Peaks pane. To hide all the peak values on the display, clear this check box. To show an individual peak, select the check box directly to the left of its Value listing. To hide an individual peak, clear the check box directly to the left of its Value listing.

The Peaks are valid for any units of the input signal. The letter after the value associated with each measurement indicates the abbreviation for the appropriate International System of Units (SI) prefix, such as m for milli-. For example, if the input signal is measured in volts, an m next to a measurement value indicates that this value is in units of millivolts.

Visuals — Array Plot Properties

The Visuals—Array Plot Properties dialog box controls various properties about the Array Plot display. From the Array Plot menu, select View > Configuration Properties to open this dialog box.

Main Pane

The Main pane of the Visuals—Array Plot Properties dialog box appears as follows.

Sample increment

Specify the spacing between samples along the x-axis as a finite numeric scalar value.

X-offset

Specify the offset to apply to the x-axis. This property is a numeric scalar. This property is Tunable.

X-axis scale

Specify 'Linear' or 'Log' as the x-axis scale . If XOffset is a negative value, you cannot set XScale to 'Log'. Tunable

Maximize axes

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

• Auto — In this mode, the axes appear maximized only if the Title and YLabel properties are empty. If you enter any value for either of these properties, the axes are not maximized.

• On — In this mode, the axes appear maximized. Any values entered into the Title and YLabel properties are hidden.

• Off — In this mode, none of the axes appear maximized.

This property is Tunable.

Display Pane

The Display pane of the Visuals—Array Plot Properties dialog box appears as follows.

Title

Specify the display title as a character vector. Enter %<SignalLabel> to use the signal labels in the Simulink Model as the axes titles. This property is Tunable.

Show legend

Select this check box to show the legend in the display. The channel legend displays a name for each channel of each input signal. When the legend appears, you can place it anywhere inside the scope window. To turn off the legend, clear the Show legend check box. If the signal has multiple channels, the scope uses an index number to identify each signal channel. You can edit the name of any channel by double-clicking the current channel name and entering a new name. Tunable

Show grid

When you select this check box, a grid appears in the display of the scope figure. To hide the grid, clear this check box. Tunable

Plot signals as magnitude and phase

When you select this check box, the scope splits the display into a magnitude plot and a phase plot. By default, this check box is cleared. If the input signal has complex values, the scope plots the real and imaginary portions on the same axes. These real and imaginary portions appear as different-colored lines on the same axes, as shown in the following figure.

Selecting this check box and clicking the Apply or OK button changes the display. The magnitude of the input signal appears on the top axes and its phase, in degrees, appears on the bottom axes. See the following figure.

This feature is useful for complex-valued input signals. If the input is a real-valued signal, selecting this check box returns the absolute value of the signal for the magnitude. The phase is 0 degrees for nonnegative input and 180 degrees for negative input. Tunable

X-label

Specify the text for the scope to display below the x-axis. This property is Tunable.

Y-label

Specify the text for the scope to display to the left of the y-axis. Tunable

Y-limits (Minimum)

Specify the minimum value of the y-axis. Tunable

Y-limits (Maximum)

Specify the maximum value of the y-axis. Tunable

Style Dialog Box

In the Style dialog box, you can customize the style of displays. You are able to change the color of the figure containing the displays, the background and foreground colors of display axes, and properties of lines in a display. From the scope menu, select View > Style to open this dialog box.

Properties

The Style dialog box allows you to modify the following properties of the scope figure:

Figure color

Specify the color that you want to apply to the background of the scope figure. By default, the figure color is gray.

Plot type

Specify the type of plot to use for all the input signals displayed in the scope window.

• When you set this property to 'Stem' , the scope displays the input signal as circles with vertical lines extending down to the x-axis at each of the sampled values . This approach is similar to the functionality of the MATLAB stem function.

• When you set this property to 'Line' , the scope displays the input signal as lines connecting each of the sampled values. This approach is similar to the functionality of the MATLAB line or plot function.

• When you set this property to 'Stairs', the scope displays the input signal as a stairstep graph. A stairstep graph is made up of only horizontal lines and vertical lines. Each horizontal line represents the signal value for a discrete sample period and is connected to two vertical lines. Each vertical line represents a change in values occurring at a sample. This approach is equivalent to the MATLAB stairs function. Stairstep graphs are useful for drawing time history graphs of digitally sampled data.

This property is Tunable.

The default setting is Stem.

Axes colors

Specify the color that you want to apply to the background of the axes.

Properties for line

Specify the channel for which you want to modify the visibility, line properties, and marker properties.

Visible

Specify whether the selected channel should be visible. If you clear this check box, the line disappears.

Line

Specify the line style, line width, and line color for the selected channel.

Marker

Specify marks for the selected channel to show at its data points. This parameter is similar to the Marker property for plot objects. You can choose any of the marker symbols from the dropdown.

Tools — Plot Navigation Properties

The Tools—Plot Navigation Properties dialog box allows you to automatically zoom in on and zoom out of your data. You can also scale the axes of the scope. In the scope menu, select Tools > Axes Scaling Properties to open this dialog box.

Properties

The Tools—Plot Navigation Properties dialog box appears as follows.

Axes Scaling

Specify when the scope automatically scales the axes. You can select one of the following options:

• Manual — When you select this option, the scope does not automatically scale the axes. You can manually scale the axes in any of the following ways:

  • Select Tools > Axes Scaling Properties.

  • Press one of the Scale Axis Limits toolbar buttons.

  • When the scope figure is the active window, press Ctrl and A simultaneously.

• Auto — When you select this option, the scope scales the axes as needed, both during and after simulation. Selecting this option shows the Do not allow Y-axis limits to shrink check box.

• After N Updates — Selecting this option causes the scope to scale the axes after a specified number of updates. This option is useful and more efficient when your scope display starts with one axis scale, but quickly reaches a different steady state axis scale. Selecting this option shows the Number of updates edit box.

By default, this property is set to Auto. This property is Tunable.

By default, this parameter is set to Manual.

Do not allow Y-axis limits to shrink

When you select this property, the y-axis is allowed only to grow during axes scaling operations. If you clear this check box, the y-axis or color limits may shrink during axes scaling operations.

This property appears only when you select Auto for the Axis scaling property. When you set the Axes scaling property to Manual or After N Updates, the y-axis or color limits are allowed to shrink. Tunable.

Number of updates

Specify as a positive integer the number of updates after which to scale the axes, or for the spectrogram, the color. This property appears only when you select After N Updates for the Axes scaling or Color scaling property. Tunable.

Scale axes limits at stop

Select this check box to scale the axes when the simulation stops. The y-axis is always scaled. The x-axis limits are only scaled if you also select the Scale X-axis limits check box.

Y-axis Data range (%)

Set the percentage of the y-axis that the scope uses to display the data when scaling the axes. Valid values are from 1 through 100. For example, if you set this property to 100, the Scope scales the y-axis limits such that your data uses the entire y-axis range. If you then set this property to 30, the scope increases the y-axis range such that your data uses only 30% of the y-axis range. Tunable.

Y-axis Align

Specify where the scope aligns your data along the y-axis when it scales the axes. You can select Top, Center, or Bottom. Tunable.

Autoscale X-axis limits

Check this box to allow the scope to scale the x-axis limits when it scales the axes. If Axes scaling is set to Auto, checking Autoscale X-axis limits only scales the data currently within the axes, not the entire signal in the data buffer. If Autoscale X-axis limits is on and the resulting axis is greater than the span of the scope, trigger position markers will not be displayed. Triggers are controlled using the Trigger Measurements panel. Tunable.

X-axis Align

Specify how the scope aligns your data along the x-axis: Left, Center, or Right. This property appears only when you select the Scale X-axis limits check box. Tunable.

See Also

dsp.LogicAnalyzer | dsp.SpectrumAnalyzer | dsp.TimeScope