11.6 The Differentiate Gadget


Overview

The Differentiate Gadget provides a convenient way to calculate and display the derivative curves in the ROI (Region of Interest) range.

Differentiate Gadget.png

With this gadget, you can:

  • Move and resize the region of data to differentiate.
  • Specify the desired derivative order.
  • View the derivative curve alongside a graph of the data.
  • Output the derivative curve to a worksheet.
To Use Differentiate Gadget

To use this tool, select Gadgets: Differentiate from the Origin menu, when a graph is active.

Dialog Settings

This dialog can be opened from the Origin menu, under Gadgets: Differentiate, or you can select Preferences from the ROI fly-out menu.

ROI Box Show Tool Name
Specify whether to show the tool's name near the top of the ROI.

Fill Color

Specify the ROI fill color.

Derivative Line Color

Specify the line color of the derivative curve.
Derivative Order Specify the derivative order. Besides this option, you can also bring up the first and second derivative curves from the fly-out menu of the ROI tool.
Smooth Savitzky-Golay Smooth
Check this check box to apply Savitzky-Golay smoothing, which performs a local polynomial regression around each point to find the derivatives.

Polynomial Order

Specifies the polynomial order for Savitzky-Golay smoothing. Note that this value cannot be smaller than the derivative order.

Points of Window

Specifies the number of points in the moving window used in the Savitzky-Golay smoothing.

The Fly-Out Menu

Click the triangle button ROI menu.png near the top right corner of the ROI to open a fly-out menu that offers the following options:

Delete ROI and Leave Derivative Graph This option will close the differentiate tool but keep the derivative curves window.
Keep Derivative Graph when Close ROI Specify whether to delete the derivative curve window if you close the tool by clicking the "x" button in the top right corner of the ROI.
Change Data Select the source data set. This is can be used only when there are multiple curves in the graph. By default, all plots in current layer will be selected. You can clear the selections ahead All Plots and Individual plots to customize the input data.

In the flyout menu, it will show first 20 datasets/plots. If there are more than 20 plots in the graph, you can click More... at the bottom of the list to open the Select Plot(s) dialog to select other plots.

Expand to Full Plot Range Expand the ROI to the full plot range.
Show 1st/2nd Derivative Show the first or second derivative curve.
Save Theme Save the settings as a theme.
Load Theme Load theme settings.
Preferences Open the Differentiate Preferences dialog.

Example

  1. Create a new worksheet and import the data HiddenPeaks.dat from the folder <Origin Program Folder>\Samples\Spectroscopy. Highlight Column B and click Button Line.png on the 2D Graphs toolbar to create a line plot.
  2. Select Gadgets: Differentiate from the Origin menu to open the settings dialog of the tool. Select 2 for Derivative Order. Keep the other default settings and click OK. A yellow ROI region is added to the plot, and a Preview window is created to show both the source and derivative curves.
    Differentiate Gadget 001.png
  3. Move the ROI and see how the derivative curve changes.