15.3.5.4 Fitting Multiple Peaks with the Multiple Peak Fit Tool

The Multiple Peak Fit tool provides an interactive and easy way to pick multiple peaks in a graph and then fit them with a peak function.

Select Analysis: Peak and Baseline: Multiple Peak Fit from the main menu. This will open the nlfitpeaks dialog.

Nlfitpeaks dialog.png

In the dialog, select the input data and the peak function for performing the fit. Note that the input data is initialized to the active data plot when the tool is launched from a graph window.
Please note, since Origin 2020b, if you started from a graph window, you can click the arrow button after this box to select Use X Scale Range to apply the X scale range on the source graph to the input range

Upon clicking the OK button, the dialog will close and the graph will be active. If the tool was launched from a worksheet, a graph will be created. The cursor will change to Accross cursor.png and the Get Points dialog will open. Use the mouse, or arrow keys on the keyboard to move the cursor to a desired peak center location. Then double-click or press Enter to select that point as a peak center. When you move the cursor, its X and Y coordinate values are displayed in the Get Points dialog and also in the Data Display window. The Get Points dialog also displays the number of peak centers selected.

Pick peaks.png

In some case, you might need use Quick Peaks gadget to find the target peaks in advance. Then, you can tag the peaks with Peak Markers firstly.

Once there are peak markers on the graph, the check box Use Peak Marker will be available. Check this check box to fit the peaks with markers directly. In this case, you don't need manually pick peaks as above.

Nlfitpeaks dialog 2.png

Once you have selected the desired number of peak centers, you have two options to proceed:

  • Press the Fit button in the Get Points dialog
    This will fit the data using your selected points to initialize the peaks, and a table with fit results and parameter values will be added to the graph.
  • Press the Open NLFit button in the Get Points dialog
    This will open the NLFit dialog where the peak function parameters such as peak height and peak center are initialized using the peak centers selected by you. You can further customize the setting such as applying bounds or constraints, or sharing of parameters, and then proceed manually with the fitting process. For detailed information about controlling the fit process, please refer to The NLFit Dialog Box.

For more advanced peak fitting including baseline detection, please use the peak fitting option in the Peak Analyzer tool, available in OriginPro.

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