Peak Finder Measurements Panel

Note

Peak Finder measurements require 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 peaks. This panel allows you to modify the settings for peak threshold, maximum number of peaks, and peak excursion.

• From the menu, select Tools > Measurements > Peak Finder.

• On the toolbar, click the Peak Finder button.

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 findpeaks (Signal Processing Toolbox) function reference.

Properties to set:

• 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. Peak excursion is illustrated alongside peak threshold in the following figure.

  

  The peak threshold is a minimum value necessary for a sample value to be a peak. The peak excursion is the minimum difference between a peak sample and the samples to its left and right in the time domain. In the figure, the green vertical line illustrates the lesser of the two height differences between the labeled peak and its neighboring samples. This height difference must be greater than the Peak Excursion value for the labeled peak to be classified as a peak. Compare this setting to peak threshold, which is illustrated by the red horizontal line. The amplitude must be above this horizontal line for the labeled peak to be classified as a peak.

  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, you must first 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 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 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 or hide all the peak values on the display, use the check box in the top-left corner of the Peaks pane.

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.