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Page Revision: 2014/12/26 07:53

The element allows to read, analyze and plot a real-time signal that is provided by the signal acquisition elements in EventIDE.

Table of Contents [Hide/Show] Description Snapshots Practical Use     Preparing the element     Technique 2 Element' actions aligned with epochs of the parent event Notes Properties     Generic Properties

Description ¶

The signal acquisition elements, e.g. OpenViBE Signal, communicate with hardware and buffer incoming data samples at the background of the experiment. In order to access the buffered data, you can use Signal Analyzer. The element operates on a single signal and allows to read, analyze and plot the signal data. The analysis is performed cyclically, within the analysis window that embraces the selected number of recent samples. The analysis returns the descriptive statistics of the 'windowed' signal: mean, min, max and standard deviation. Other estimates should be done manually, hence the element allows reading the signal samples as array of double numbers. When signal monitoring is required, the element can generate a live plot, which can be placed to the Status Screen.

Snapshots ¶

Snapshot 1

Practical Use ¶

Preparing the element ¶

1. Make sure that your experiment contains one of the data acquisition elements, e.g. OpenViBE Signal element
2. Prepare the data acquisition element such that it is set to collect at least one signal channel.
3. Add new Signal Analyzer element to the event, where you plan to process the signal (the element operates only within the parent event).
4. Select the added element to browse its properties in the Property panel.
5. Define a signal for processing, via the 'Selected Signal' property.
6. Adjust the 'Sampling Rate' property such that the value matches to a real sampling rate of the selected signal.
7. Choose the size of the analysis window via the corresponding property.
8. Select the 'signal normalization' procedure, if required.
9. If you want to filter the signal for plotting, turn on the bandpass filtering in the 'Bandpass Filter' group and adjust the filter parameter
   

Technique 2 ¶

1. Step 1
2. Step 2
   

 // Check the trial outcome. Result and RT just other user variables
// insert code snippet here..

Element' actions aligned with epochs of the parent event ¶

Epoch	Actions
After Onset	The element starts analyzing the selected signal
Control Loop step	Latest signal samples is analyzed within the selected analysis window and the signal plot gets updated.
Before Offset	The element stops analyzing the selected signal

Notes ¶

• The bandpass filtering affects only signal plotting, not the signal analysis.
  

Properties ¶

Generic Properties ¶

Name	Description	Constraints	Value Type	Upon Runtime Change
Signal Source
Selected Signal	Defines the signal for processing by the element. The signals are provided by the data acquisition elements.	Design Time..	String
Sampling Rate	Defines the sampling rate of the original signal, in Hz	Design Time..	Int32
Analysis Window Size	Defines the size (in samples) of the moving analysis window for signal processing.	Design Time..	Int32
Signal Normalization	Defines the normalization procedure that is automatically applied to the signal before the analysis	Normal..	enumeration	The selected procedure is applied on the next analysis cycle
Bandpass Filter
Is Filtering	Defines whether the Butterworth bandpass filter is applied in signal plotting. This filter does not affect the signal analysis.	Normal..	Boolean
Filter Order	Defines the order of the Butterworth bandpass filter	Normal..	Int32
Low CutOff	Defines the low cutoff of the Butterworth bandpass filter, in Hz	Normal..	Double
High CutOff	Defines the high cut-off of the Butterworth bandpass filter, in Hz	Normal..	Double
Runtime Status
Is Running	Defines whether the analysis and plotting is going on in the present. You can use this property to temporally cease the signal processing for a sake of performance.	Normal..	Boolean
XAML Signal Plot	Returns a live XAML signal plot with the signal data. The plot can be used for direct binding to the Content property of the XAML ContentControl element, e.g. The ContentControl with a generated plot can be shown on the status screen or by the XAML Layout element.	Status..	XAML UIElement
Signal Samples	Returns an double array of the newest signal samples. The array length is equal to the size of the analysis window. The values are updated on every Control Loop cycle of the parent event. The last item in the array corresponds to the most recent signal sample.	Status..	double[]
Plotting
Plot Title	Defines the title of the generated signal plot	Normal..	String	The signal plot is updated
Plot Theme	Defines a visual theme of the generated signal plot	Normal..	enum	The signal plot is updated
Line Thickness	Defines the thickness of the data line on the generated signal plot	Normal..	Double	The signal plot is updated
Line Color	Defines the color of the data line on the generated signal plot	Normal..	stColor	The signal plot is updated
Max Y-Axis	Defines the range of the Y-axis (power) on the generated signal plot. Zero value denotes the auto-range.	Normal..	Double	The signal plot is updated
Rendering Size	Defines the size of the generated plot in pixels. The plot is automatically stretched on rendering, but a larger rendering size improves the chart quality with some cost in performance. The rendering size is also used as the resulting image resolution, when the plot is exported into a file.	Design Time..	clSize
Signal Statistics
Mean	Returns the means of the signal values within the analysis window	Status..	double
Minimum	Returns the minimum of the signal values within the analysis window	Status..	double
Maximum	Returns the maximum of the signal values within the analysis window	Status..	double
Standard Deviation	Returns the standard deviations of the signal values within the analysis window	Status..	double

+=== Properties inherited from clElement === Inherited properties of clElement

Name	Description	Constraints	Value Type	Upon Change
Control
Is Enabled	If set to false the element is completely omitted when the experiment is run.	Design Time..	Boolean
Title	Title of the element.	Design Time..	String